Ion beam device

ABSTRACT

An ion beam device according to the present invention includes a gas field ion source including an emitter tip supported by an emitter base mount, a ionization chamber including an extraction electrode and being configured to surround the emitter tip, and a gas supply tube. A center axis line of the extraction electrode overlaps or is parallel to a center axis line of the ion irradiation light system, and a center axis line passing the emitter tip and the emitter base mount is inclinable with respect to a center axis line of the ionization chamber. Accordingly, an ion beam device including a gas field ion source capable of adjusting the direction of the emitter tip is provided.

This is a continuation of U.S. application Ser. No. 14/328,754, filed onJul. 11, 2014, which is a continuation of U.S. application Ser. No.12/995,700, filed on Mar. 10, 2011, now U.S. Pat. No. 8,779,380, whichis a 371 National Stage of PCT/JP2009/056485, filed Mar. 30, 2009, whichclaims priority to JP 2008-148392, filed Jun. 5, 2008. The entiredisclosures of all of these applications are hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to an ion beam device such as an ionmicroscope and an ion beam processing device, a combined device of theion beam processing device and the ion microscope, and a combined deviceof the ion microscope and an electron microscope. The present inventionalso relates to an analyzing and examining device applied with the ionmicroscope and the electron microscope.

The entire contents of all citations, patents, and patent applicationscited in the present specification are hereby incorporated in thepresent specification by reference.

BACKGROUND ART

The structure of a sample surface can be observed by irradiating thesample with an electron while scanning and detecting secondary chargedparticles released from the sample. This is called a scanning electronmicroscope (hereinafter abbreviated as SEM). The structure of the samplesurface can be observed even by irradiating the sample with an ion beamwhile scanning and detecting secondary charged particles released fromthe sample. This is called a scanning ion microscope (hereinafterabbreviated as SIM). In particular, if the sample is irradiated with theion species of light mass such as hydrogen and helium, the sputteringaction becomes relatively small and it becomes suitable for observingthe sample.

Furthermore, the ion beam has a characteristic of being sensitive toinformation on the sample surface compared to the electron beam. This isbecause an excitation region of the secondary charged particle islocalized by the sample surface compared to the irradiation of theelectron beam. Aberration is generated by a diffraction effect in theelectron beam as the property for the wave of the electron cannot beignored. The diffraction effect can be ignored in the ion beam as theion beam is heavy compared to the electron.

The information reflecting the structure of the inside of the sample canbe obtained by irradiating the sample with the ion beam, and detectingthe ion transmitted through the sample. This is called a transmissionion microscope. In particular, if the sample is irradiated with the ionspecies of light mass such as hydrogen and helium, it becomes suitablefor observation as the proportion of the ion that transmits through thesample becomes large.

On the contrary, irradiating the sample with the ion species of heavymass such as argon, xenon, and gallium is suitable for processing thesample by the sputtering action. In particular, a focused ion beamdevice (hereinafter referred to as FIB) using a liquid metal ion source(hereinafter referred to as LMIS) is known as an ion beam processingdevice. Furthermore, a combined FIB-SEM device of the scanning electronmicroscope (SEM) and the focused ion beam (FIB) is also used in recentyears. In the FIB-SEM device, the FIB is irradiated to form a squarehole at the desired area so that the cross-section can be SEM observed.The sample can be processed even by generating a gas ion such as argonand xenon with a plasma ion source and a gas field ion source, andirradiating the sample with the same.

In the ion microscope, the gas field ion source is suitable for the ionsource. The gas field ion source can generate an ion beam having anarrow energy width. Furthermore, the ion generation source can generatea microscopic ion beam since the size is small.

In the ion microscope, an ion beam of large current density needs to beobtained on the sample to observe the sample at a high signal/noiseratio. To this end, an ion emission angle current density of the gasfield ion source needs to be large. The molecular density of the ionmaterial gas (ionized gas) near the emitter tip merely needs to be madelarge to increase the ion emission angle current density. The gasmolecular density per unit pressure is inversely proportional to thetemperature of the gas. Thus, the emitter tip is cooled to an extremelylow temperature, and the temperature of the gas around the emitter tipis to be lowered. The molecular density of the ionized gas near theemitter tip thus can be made large. The pressure of the ionized gasaround the emitter tip can be set to about 10⁻² to 10 Pa.

However, if the pressure of the ion material gas is greater than orequal to ˜1 Pa, the ion beam collides with a neutral gas andneutralizes, whereby the ion current lowers. When the number of gasmolecules in the gas field ion source increases, the frequency of thegas molecules, the temperature of which is increased by colliding withthe vacuum chamber wall of high temperature, which collide with theemitter tip becomes high. The temperature of the emitter tip thus risesand the ion current lowers. To this end, a gas ionization chamber thatmechanically surrounds the periphery of the emitter tip is arranged inthe gas field ion source. The gas ionization chamber is formed using anion extraction electrode arranged facing the emitter tip.

Patent document 1 discloses enhancing the ion source characteristics byforming a microscopic projection at the distal end of the emitter tip.Non-patent document 1 discloses forming the microscopic projection atthe distal end of the emitter tip using a second metal different fromthe material of the emitter tip. Non-patent document 2 discloses ascanning ion microscope mounted with the gas field ion source for ionreleasing helium.

Patent document 2 discloses a gas field ion source in which a bellows isarranged in the ionization chamber. However, in such gas field ionsource, the problem in which the ionization chamber is contacted to roomtemperature through a sample chamber wall, and the gas supplied to theionization chamber collides with the sample chamber wall of hightemperature is not mentioned. The description related to the inclinationof the emitter tip is also not made.

Patent document 3 discloses a gas field ion source arranged with adirection adjustment mechanism for varying the axis direction of the ionsource. However, in such gas field ion source, the problem in which theionization chamber is contacted to room temperature through a samplechamber wall, and the gas supplied to the ionization chamber collideswith the sample chamber wall of high temperature is not mentioned.Furthermore, the extraction electrode inclines with the change in axisdirection of the ion source.

Patent document 4 discloses a gas field ion source arranged with aswitching switch for connecting an extraction electrode high voltagelead-in wire to an emitter tip high voltage lead-in wire. In such gasfield ion source, the discharge between the emitter tip and theextraction electrode can be prevented after the so-called conditioningprocess or an enforced discharging process between the ion source outerwall and the emitter tip.

Patent document 5 discloses a charged beam device in which a vibrationproofing tool is arranged between a base plate for mounting the mainbody of the charged particle device and a device mount. However, thedescription related to a cooling mechanism of the charged particlesource is not made at all in patent document 5.

Patent document 6 proposes a device for observing and analyzing defects,foreign substances, and the like by forming a square hole in thevicinity of an abnormal area of a sample with the FIB and observing thecross-section of the square hole with the SEM device. Patent document 7proposes a technique of extracting a microscopic sample for transmissionelectron microscope observation from a bulk sample using the FIB and theprobe.

-   Patent document 1: Japanese Laid-Open Patent Publication No.    58-85242-   Patent document 2: Japanese Patent Publication NO. 3-74454-   Patent document 3: Japanese Laid-Open Patent Publication No.    62-114226-   Patent document 4: Japanese Laid-Open Patent Publication No.    1-221847-   Patent document 5: Japanese Laid-Open Patent Publication No.    8-203461-   Patent document 6: Japanese Laid-Open Patent Publication No.    2002-150990-   Patent document 7: International Patent Publication WO99/05506-   Non-patent document 1: H.-S. Kuo, I.-S. Hwang, T.-Y. Fu, J.-Y. Wu,    C.-C. Chang, and T. T. Tsong, Nano Letters 4 (2004) 2379.-   Non-patent document 2: J. Morgan, J. Notte, R. Hill, and B. Ward,    Microscopy Today, Jul. 14 (2006) 24

DISCLOSURE OF THE INVENTION

The gas field ion source including the gas ionization chamber of theprior art has the following problems. Some emitter tips have anano-pyramid structure in which a microscopic projection is arranged atthe distal end. In the emitter tip having such structure, the spread ofthe angle at which the ion beam is released is only about one degree.The direction of the emitter tip needs to be adjusted in order toirradiate a predetermined position of the sample with such microscopicion beam. The direction of the emitter tip cannot be easily adjustedsince the gas ionization chamber has a fixed structure. Thus anattachment portion of the emitter tip needed to be mechanicallyadjusted. The direction of the extraction electrode also changes whenthe position and the direction of the emitter tip are adjusted.

The inventors of the present invention found that a slight inclinationof the extraction electrode influences the focusing performance of theion beam. In other words, a problem in that the resolution of the sampleobservation degrades by the slight inclination of the extractionelectrode was found.

Furthermore, the gas ionization chamber is not a sealed chamber althoughit has a structure of surrounding the emitter tip using the ionextraction electrode. The ionized gas supplied to the gas ionizationchamber thus inevitably leaks. When the ionized gas leaks, the pressureof the ion material gas around the emitter tip lowers, and the ioncurrent lowers. However, no measures have been taken in the prior artfor the leakage of the ionized gas from the gas ionization chamber.

In the ion microscope mounted with the gas field ion source, a coolingmechanism for cooling the emitter tip to an extremely low temperature isarranged. Such cooling mechanism includes a vibration source such as arefrigerator pump and a compressor. When the vibration from suchvibration source is transmitted to the emitter tip, the sampleobservation of high resolution becomes impossible.

It is an object of the present invention to provide an ion beam deviceincluding a gas field ion source that can adjust the position and thedirection of the emitter tip, and that contributes to enhancing the ionsource luminance and enhancing the focusing performance of the ion beam.

It is another object of the present invention to provide an ion beamdevice in which the vibration from the cooling mechanism for the gasfield ion source reduces the vibration of the emitter tip enabling thesample observation of high resolution.

It is another further object of the present invention to provide adevice for forming a cross-section by processing with an ion beam andobserving the cross-section with an ion microscope in place of a devicefor forming a cross-section by processing the sample with the ion beamand observing the cross-section with an electron microscope, and amethod of observing the cross-section.

It is also another further object of the present invention to provide adevice that enables the sample observation by the ion beam device, thesample observation by the electron microscope, and an element analysiswith one device, an analyzer for observing and analyzing defects,foreign substances, and the like, and an examining device.

According to the present invention, the ion beam device includes a gasfield ion source for generating an ion beam, an ion irradiation lightsystem for guiding the ion beam from the gas field source to a sample,and a vacuum chamber for accommodating the gas field ion source and theion irradiation light system.

The gas field ion source includes an emitter tip for generating theions, an emitter base mount for supporting the emitter tip, a gasionization chamber including an extraction electrode arranged facing theemitter tip and being configured to surround the emitter tip, and a gassupply tube for supplying gas to the vicinity of the emitter tip; and acenter axis line passing the emitter tip and the emitter base mount isinclinable with respect to a center axis line of the ionization chamber.

According to the present invention, the ion beam device includes the gasfield ion source, the vacuum chamber, and the base plate for supportingthe sample chamber, where the base plate includes a vibration proofingmechanism for reducing vibration from being transmitted to the gas fieldion source, the vacuum chamber, and the sample chamber.

According to the present invention, an ion beam device including a gasfield ion source capable of adjusting the position and the direction ofthe emitter tip is provided.

According to the present invention, an ion beam device in whichvibration from a cooling mechanism for the gas field ion source does notinfluence the emitter tip is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration view of a first example of an ionmicroscope according to the present invention.

FIG. 2 is a schematic configuration view of a control system of a firstexample of the ion microscope according to the present invention.

FIG. 3 is a schematic configuration view of a cooling mechanism of a gasfield ion source of the first example of the ion microscope according tothe present invention.

FIG. 4 is a schematic configuration view of the gas field ion source ofthe first example of the ion microscope according to the presentinvention.

FIG. 5 is a schematic configuration view of a gas molecule ionizationchamber of the gas field ion source of the first example of the ionmicroscope according to the present invention.

FIG. 6A is a schematic view of the periphery of an emitter tip beforethe inclination of the emitter tip of the gas field ion source of thefirst example of the ion microscope according to the present invention.

FIG. 6B is a schematic view of the periphery of the emitter tip afterthe inclination of the emitter tip of the gas field ion source of thefirst example of the ion microscope according to the present invention.

FIG. 7 is a schematic configuration view of a second example of the ionmicroscope according to the present invention.

FIG. 8 is a schematic configuration view of a third example of the ionmicroscope according to the present invention.

FIG. 9 is a schematic configuration view of a fourth example of the ionmicroscope according to the present invention.

FIG. 10A is a view describing the operation of an open/close valve (openstate) of the gas molecule ionization chamber of the gas field ionsource of a fifth example of the ion microscope according to the presentinvention.

FIG. 10B is a view describing the operation of the open/close valve(close state) of the gas molecule ionization chamber of the gas fieldion source of the fifth example of the ion microscope according to thepresent invention.

FIG. 11A is a view describing the operation of a disconnecting mechanism(connected state) of the wiring at the periphery of the gas moleculeionization chamber of the gas field ion source of a sixth example of theion microscope according to the present invention.

FIG. 11B is a view describing the operation of a disconnecting mechanism(disconnected state) of the wiring at the periphery of the gas moleculeionization chamber of the gas field ion source of the sixth example ofthe ion microscope according to the present invention.

FIG. 12 is a schematic configuration view of a seventh example of theion microscope according to the present invention.

DESCRIPTION OF SYMBOLS

-   1 gas field ion source-   2 ion beam irradiation system column-   3 sample chamber-   4 cooling mechanism-   5 condenser lens-   6 beam limiting aperture-   7 beam scanning electrode-   8 objective lens-   9 sample-   10 sample stage-   11 secondary particle detector-   12 ion source vacuum exhaust pump-   13 sample chamber vacuum exhaust pump-   14 ion beam-   14A optical axis-   15 gas molecule ionization chamber-   16 compressor-   17 device mount-   18 base plate-   19 vibration proofing mechanism-   20 floor-   21 emitter tip-   22 filament-   23 filament mount-   24 extraction electrode-   25 gas supply piping-   26 supporting rod-   27 hole-   28 side wall-   29 top plate-   30 resistive heater-   31 opening-   32 lid member-   33 operation rod-   34 lid member-   40 refrigerator-   40A center axis line-   41 main body-   42A, 42B stage-   43 pot-   46 helium gas-   51 upper flange-   52 sapphire base-   53 cooling conduction rod-   54 copper stranded wire-   55 sapphire base-   56 copper stranded wire-   57 cooling conduction pipe-   58 shield reducing the thermal radiation-   59 electrostatic lens-   60 electrode-   61, 62 bellows-   63 insulating material-   64 emitter base mount-   68 vacuum chamber-   69 bellows-   81 liquid or solid nitrogen chamber-   82 liquid or solid nitrogen tank-   83 vacuum exhaust port-   84 solid nitrogen-   85 supporting column-   86 bellows-   87 supporting column-   91 gas field ion source control device-   92 refrigerator control device-   93 lens control device-   94 beam limiting aperture control device-   95 ion beam scanning control device-   96 secondary electron detector control device-   97 sample stage control device-   98 vacuum exhaust pump control device-   99 calculation processing device-   101 surface plate-   102 vibration free leg-   103, 104 supporting column-   133 electric wire-   134 power supply-   135 high voltage power supply-   136 thin wire made of stainless steel-   137 disconnecting mechanism-   138 thick wire made of copper-   139 thin wire made of stainless steel-   140 disconnecting mechanism-   141 ion extraction power supply-   142 power supply-   301 scanning deflection electrode-   302 aperture plate-   303 movable emission pattern observation mechanism-   304 secondary particle-   305 secondary particle detector-   306 center line of ion irradiation system-   307 ion image detector-   308 mirror-   400 compressor unit-   401 GM refrigerator-   402 heat exchanger-   403 piping-   404 transfer tube-   405 heat exchanger-   407 piping-   408 first cooling stage-   409 heat exchanger-   410 heat exchanger-   411 second cooling stage-   412 heat exchanger-   413 piping-   414 heat exchanger-   415 piping-   416 vacuum heat insulating container-   417, 418 supporting body-   419 cover

BEST MODE FOR CARRYING OUT THE INVENTION

An example of an ion beam device according to the present invention willbe described with reference to FIG. 1. A first example of a scanning ionmicroscope device will be hereinafter described as the ion beam device.The scanning ion microscope of the present example includes a gas fieldion source 1, a column 2, a sample chamber 3, and a cooling mechanism 4.The inside of the column 2 and the sample chamber 3 is held in vacuum,and an ion beam irradiation system is arranged therein. The ion beamirradiation system includes an electrostatic condenser lens 5, a beamlimiting aperture 6, a beam scanning electrode 7, and an electrostaticobjective lens 8. A sample stage 10 for mounting a sample 9 and asecondary particle detector 11 are arranged in the sample chamber 3. Anion beam 14 from the gas field ion source 1 is irradiated onto thesample 9 through the ion beam irradiation system. The secondary particlebeam from the sample 9 is detected by the secondary particle detector11. Although not illustrated, an electron gun for neutralizing thecharge up of the sample when the ion beam is irradiated, and a gas gunfor supplying etching or deposition gas to the vicinity of the sampleare arranged.

The cooling mechanism 4 includes a refrigerator 40 for cooling the gasfield ion source 1. In the ion microscope of the present example, acenter axis line 40A of the refrigerator 40 is arranged parallel to anoptical axis 14A of the ion beam irradiation system.

The ion microscope of the present example further includes an ion sourcevacuum exhaust pump 12 for vacuum exhausting the gas field ion source 1,and a sample chamber vacuum exhaust pump 13 for vacuum exhausting thesample chamber 3.

A base plate 18 is arranged on a device mount 17 arranged on a floor 20by way of a vibration proofing mechanism 19. The gas field ion source 1,the column 2, and the sample chamber 3 are supported by the base plate18.

A supporting column 103 is arranged on the device mount 17. Therefrigerator 40 is supported by the supporting column 103. The vibrationof the refrigerator 40 is transmitted to the device mount 17 through thesupporting column 103. However, the vibration of the refrigerator 40 isreduced by the vibration proofing mechanism 19 and transmitted to thebase plate 18. Therefore, the vibration of the refrigerator 40 is barelytransmitted to the gas field ion source 1, the ion beam irradiationsystem column 2, and the sample chamber 3 through the supporting column103, whereby high resolution performance of the scanning ion beammicroscope is realized.

A compressor unit (compressor) 16 having helium gas etc. as an operationgas is installed on the floor 20 to supply the helium gas of highpressure to a Gifford-McMahon (GM) refrigerator 40 through a piping 111.The coldness is generated when the helium gas of high pressure isperiodically expanded inside the GM refrigerator, and the low pressurehelium gas, which became low pressure by expansion, is collected by thecompressor unit through a piping 112.

The vibration of the compressor unit (compressor) 16 is transmitted tothe device mount 17 through the floor 20. A vibration proofing mechanism19 is arranged between the device mount 17 and the base plate 18, sothat the vibration of high frequency of the floor is less likely to betransmitted to the gas field ion source 1, the ion beam irradiationsystem column 2, the sample chamber (vacuum sample chamber) 3, and thelike. Therefore, the vibration of the compressor unit (compressor) 16 isless likely to be transmitted to the gas field ion source 1, the ionbeam irradiation system column 2, and the sample chamber 3 through thefloor 20. The refrigerator 40 and the compressor 16 have been describedhere as causes for the vibration of the floor 20. However, the causesfor the vibration of the floor 20 are not limited thereto.

The vibration proofing mechanism 19 may be configured by a vibrationproofing rubber, spring, damper, or a combination thereof. The baseplate 18 includes a supporting column 104. The lower part of the coolingmechanism 4 is supported by the supporting column 104, which will behereinafter described with reference to FIG. 3.

In the present example, the vibration proofing mechanism 19 is arrangedabove the device mount 17, but the vibration proofing mechanism 19 maybe arranged at the leg of the device mount 17 or may be arranged at bothplaces simultaneously.

FIG. 2 shows an example of a control device of an ion microscopeaccording to the present invention shown in FIG. 1. The control deviceof the present example includes a gas field ion source control device 91for controlling the gas field ion source 1, a refrigerator controldevice 92 for controlling the refrigerator 40, a lens control device 93for controlling the condenser lens 5, a beam limiting aperture controldevice 94 for controlling the beam limiting aperture 6, an ion beamscanning control device 95 for controlling the beam scanning electrode7, a secondary electron detector control device 96 for controlling thesecondary particle detector 11, a sample stage control device 97 forcontrolling the sample stage 10, a vacuum exhaust pump control device 98for controlling the sample chamber vacuum exhaust pump 13, and acalculation processing device 99 for performing various types ofcalculations. The calculation processing device 99 includes an imagedisplay unit. The image display unit displays images generated from adetection signal of the secondary particle detector 11, and informationinput by the input means.

The sample stage 10 includes a mechanism for linearly moving the sample9 in two orthogonal directions within a sample mounting surface, amechanism for linearly moving the sample 9 in a direction perpendicularto the sample mounting surface, and a mechanism for rotating the sample9 within the sample mounting surface. The sample stage 10 furtherincludes an inclination function capable of varying the irradiationangle of the ion beam 14 to the sample 9 by rotating the sample 9 aboutan inclination axis. Such controls are executed by the sample stagecontrol device 97 according to a command from the calculation processingdevice 99.

The operation of the ion beam irradiation system of the ion microscopeof the present example will now be described. The operation of the ionbeam irradiation system is controlled by a command from the calculationprocessing device 99. The ion beam 14 generated by the gas field ionsource 1 is converged by the condenser lens 5 with the beam diameterlimited by the beam limiting aperture 6, and focused by the objectivelens 8. The focused beam is irradiated on the sample 9 on the samplestage 10 while being scanned.

The secondary particles released from the sample are detected by thesecondary particle detector 11. The signal from the secondary particledetector 11 is luminance-modulated and sent to the calculationprocessing device 99. The calculation processing device 99 generates ascanning ion microscope image and displays the same on the image displayunit. The high resolution observation of the sample surface is therebyrealized.

FIG. 3 shows an example of the configuration of the gas field ion source1 and the cooling mechanism 4 thereof of the ion microscope according tothe present invention shown in FIG. 1. The gas field ion source 1 willbe described in detail in FIG. 4. The cooling mechanism 4 will bedescribed here. In the present example, a cooling mechanism in which theGM refrigerator 40 and a helium gas pot 43 are combined is used for thecooling mechanism 4 of the gas field ion source 1. The center axis lineof the GM refrigerator is arranged parallel to an optical axis of theion beam irradiation system passing the emitter tip 21 of the ionmicroscope. Both the enhancement of the focusing property of the ionbeam and the enhancement of the refrigerating function are thusrealized.

The GM refrigerator 40 includes a main body 41, a first cooling stage42A, and a second cooling stage 42B. The main body 41 is supported bythe supporting column 103. The first cooling stage 42A and the secondcooling stage 42B have a structure of being suspended from the main body41.

The outer diameter of the first cooling stage 42A is greater than theouter diameter of the second cooling stage 42B. The refrigeratingability of the first cooling stage 42A is about 5 W, and therefrigerating ability of the second cooling stage 42B is about 0.2 W.The first cooling stage 42A is cooled up to about 50 K. The secondcooling stage 42B can be cooled up to 4 K.

The upper end of the first cooling stage 42A is surrounded by a bellows69. The lower end of the first cooling stage 42A and the second coolingstage 42B are covered by a gas tight pot 43. The pot 43 includes aportion 43A of large diameter configured to surround the first coolingstage 42A, and a portion 43B of small diameter configured to surroundthe second cooling stage 42B. The pot 43 is supported by the supportingcolumn 104. As shown in FIG. 1, the supporting column 104 is supportedby the base plate 18.

The bellows 69 and the pot 43 have a sealed structure, where helium gas46 is filled therein as a thermal conductive medium. Two cooling stages42A, 42B are surrounded by the helium gas 46, but are not contacted tothe pot 43. Neon gas or hydrogen may be used in place of the helium gas.

In the GM refrigerator 40 of the present example, the first coolingstage 42A is cooled up to about 50 K. Thus, the helium gas 46 at theperiphery of the first cooling stage 42A is cooled to about 70 K. Thesecond cooling stage 42B is cooled to 4 K. The helium gas 46 at theperiphery of the second cooling stage 42B is cooled to about 6 K. Thelower end of the pot 43 is thereby cooled to about 6 K.

The vibration of the main body 41 of the GM refrigerator 40 istransmitted to the supporting column 103 and the two cooling stages 42A,42B. The vibration transmitted to the cooling stages 42A, 42B isattenuated by the helium gas 46. Although the heat is conducted as thehelium gas exists in the middle even if the cooling stages 42A, 42B ofthe GM refrigerator vibrate, the mechanical vibration is attenuated andthe vibration is difficult to be propagated to the sealed pot 43 cooledby the first cooling stage 42A and the second cooling stage 42B. Inparticular, the vibration of high number of vibrations is less likely tobe transmitted. In other words, an effect in which the mechanicalvibration of the pot 43 is reduced extremely compared to the mechanicalvibration of the cooling stages 42A, 42B of the GM refrigerator isobtained.

As described with reference to FIG. 1, the vibration of the compressor16 is transmitted to the device mount 17 through the floor 20, but isprevented from being transmitted to the base plate 18 by the vibrationproofing mechanism 19. Therefore, the vibration of the compressor 16 isnot transmitted to the supporting column 104 and the pot 43.

The lower end of the pot 43 is connected to a cooling conduction rod 53made of copper having high thermal conductivity. A gas supply piping 25is arranged inside the cooling conduction rod 53. The cooling conductionrod 53 is covered by a cooling conduction pipe 57 made of copper.

In the present example, a shield reducing the thermal radiation (notshown) is connected to the portion 43A of large diameter of the pot 43,and in turn, the shield reducing the thermal radiation is connected tothe cooling conduction pipe 57 made of copper. Therefore, the coolingconduction rod 53 and the cooling conduction pipe 57 are always held atthe same temperature as the pot 43.

The GM refrigerator 40 is used in the present example, but instead, apulse tube refrigerator or a sterling refrigerator may be used.Furthermore, the refrigerator includes two cooling stages in the presentexample, but may include a single cooling stage, and the number ofcooling stages is not particularly limited.

An example of the configuration of the gas field ion source and itsperiphery of the ion microscope according to the present invention willbe described in detail with reference to FIG. 4. The gas field ionsource of the present example includes an emitter tip 21, an extractionelectrode 24, and an electrostatic lens 59. The extraction electrode 24includes a hole through which the ion beam passes. The electrostaticlens 59 includes three electrodes in the present example, each of whichhas a center hole. The emitter tip 21 is arranged facing the extractionelectrode 24.

A scanning deflection electrode 301, an aperture plate 302, a shutter303, a secondary particle detector 305, and an ion image detector 307are arranged below the electrostatic lens 59. The ion beam passes alongthe center line 306 of the ion irradiation system.

The emitter tip 21 is suspended from an upper flange 51, where asupporting portion of the emitter tip 21 has a movable structure. Themovable structure of the emitter tip 21 will be hereinafter described indetail with reference to FIG. 6A and FIG. 6B. The extraction electrode24 is fixedly attached with respect to a vacuum chamber 68. The vacuumchamber 68 is an upper structure of the column shown in FIG. 1.

The emitter tip 21 is supported by a sapphire base 52. The sapphire base52 is connected to the cooling conduction rod 53 by way of a copperstranded wire 54 (wire in which about 1000 copper wires having adiameter of 50 micrometers are intertwined). The extraction electrode 24is supported by the sapphire base 55. The sapphire base 55 is connectedto the cooling conduction rod 53 by way of a copper stranded wire 56.Therefore, the emitter tip 21, the sapphire base 52, the copper strandedwire 54, the cooling conduction rod 53, and the pot 43 compose a heattransmission path. Similarly, the extraction electrode 24, the sapphirebase 55, the copper stranded wire 56, the cooling conduction rod 53, andthe pot 43 compose a heat transmission path.

In other words, the present cooling mechanism includes a coldnessgeneration means for generating coldness by expanding a first highpressure gas generated in the compressor unit, and a cooling mechanismfor cooling the emitter tip 21 or a body to be cooled with a second gas,which is helium gas, in the pot 43 cooled by the coldness of thecoldness generation means.

A shield reducing the thermal radiation 58 is arranged to surround theemitter tip 21 and the extraction electrode 24. The shield reducing thethermal radiation 58 reduces the heat flow-in by heat radiation to theextraction electrode 24 and the gas molecule ionization chamber. Theshield reducing the thermal radiation 58 is connected to the coolingconduction pipe 57. An electrode 60 closest to the extraction electrode24 of the three electrodes of the electrostatic lens 59 is connected tothe shield reducing the thermal radiation 58. The electrode 60, theshield reducing the thermal radiation 58, the cooling conduction pipe57, the shield reducing the thermal radiation, and the pot 43 compose aheat transmission path.

In the present example, the sapphire bases 52, 55 and the coolingconduction rod 53 are connected by deformable copper stranded wires 54,56. The copper stranded wire 54 has a function of holding the heattransmission path including the emitter tip 21, the sapphire base 52,and the cooling conduction rod 53 even if the position of the emittertip 21 is displaced. Furthermore, the copper stranded wire 54 havinghigh flexibility prevents the high frequency vibration from beingtransmitted to the sapphire base 52 and the emitter tip 21 through thecooling conduction rod 53. The copper stranded wire 56 prevents the highfrequency vibration from being transmitted to the sapphire base 55 andthe extraction electrode 24 through the cooling conduction rod 53. Thecopper stranded wire 54, which is a heat transferring member, is notlimited to copper member as long as it is a soft member having highthermal conductivity and is less likely to transmit vibration, and maybe silver stranded wire.

Therefore, in the present example, effects such as the extremely lowtemperature of the emitter tip is realized, the gas field ion source inwhich the ion beam of greater current is obtained is provided, and theion microscope enabling high resolution observation is provided areachieved.

In the gas field ion source of the present example, the extractionelectrode is fixed with respect to the vacuum chamber, but the emittertip is movable with respect to the extraction electrode. Thus, theposition adjustment of the emitter tip with respect to the hole of theextraction electrode and the axis adjustment of the emitter tip withrespect to the optical system can be carried out, and a microscopic ionbeam can be formed.

The axis adjustment of the emitter tip will now be described. A shutter302 is moved to decenter the hole formed in the shutter 302 from acenter axis line 306 of the ion beam irradiation system. The ion beam 14generated by the emitter tip 21 passes through the electrostatic lens59, passes through the scanning deflection electrode 301, and furtherpasses through the hole of the aperture plate 302 and hits the shutter302. The secondary particles 304 such as the secondary electron aregenerated from the shutter 302. The secondary particles 304 are detectedby the secondary particle detector 305 thereby obtaining a secondaryparticle image. The ion emission pattern of the emitter tip can beobserved in the secondary particle image by arranging a microscopicprojection at the upper part of the shutter 302. Alternatively, amicroscopic hole may be formed, so that when the aperture plate 302 ismechanically moved and scanned in two directions perpendicular to theion beam, the ion release pattern can be observed even by detecting thesecondary particles of when the ion beam that passed the aperture plate302 is irradiated on a different shutter plate. The position and theangle of the emitter tip are adjusted while observing the ion emissionpattern in the above manner. The shutter 302 is moved after the axisadjustment of the emitter tip. The ion beam thereby passes through thehole of the shutter 302. A movable emission pattern observationmechanism 303 can also be used. In other words, the movable emissionpattern observation mechanism 303 is moved to decenter the hole formedin the movable emission pattern observation mechanism 303 from thecenter axis line 306 of the ion beam irradiation system. An ion imagedetector 307 including a micro-channel plate and a fluorescent plate isarranged on the movable emission pattern observation mechanism 303. Theimage of the fluorescent plate can be observed with a mirror 308arranged below the ion image detector 307. In other words, the emissiondirection and the emission pattern of the ion beam can be observed.After the observation is finished, the hole formed in the movableemission pattern observation mechanism 303 is returned to the centeraxis line 306 of the ion beam irradiation system to enable the ion beamto pass through.

The configuration of the gas field ion source of the ion microscopeaccording to the present invention will be further described in detailwith reference to FIG. 5. The gas field ion source of the presentexample includes the emitter tip 21, a pair of filaments 22, a filamentmount 23, a supporting rod 26, and an emitter base mount 64. The emittertip 21 is fixed to the filament 22. The filament 22 is fixed to thesupporting rod 26. The supporting rod 26 is supported by the filamentmount 23. The filament mount 23 is fixed to the emitter base mount 64.As shown in FIG. 4, the emitter base mount 64 is attached to the upperflange 51. The emitter base mount 64 and the shield reducing the thermalradiation 58 or the vacuum chamber 68 are connected by a bellows 61.

The gas field ion source of the present example also includes anextraction electrode 24, a cylindrical resistive heater 30, acylindrical side wall 28, and a top plate 29. The extraction electrode24 is arranged facing the emitter tip 21, and includes a hole 27 throughwhich the ion beam 14 passes. The top plate 29 is connected with aninsulating material 63. A bellows 62 is attached between the insulatingmaterial 63 and the filament mount 23.

The side wall 28 and the top plate 29 surround the emitter tip 21. Aspace surrounded by the extraction electrode 24, the side wall 28, thetop plate 29, the bellows 62, the insulating material 63, and thefilament mount 23 is called the gas molecule ionization chamber 15.

The gas supply piping 25 is connected to the gas molecule ionizationchamber 15. The ion material gas (ionized gas) is supplied to theemitter tip 21 by the gas supply piping 25. The ion material gas(ionized gas) is helium or hydrogen.

The gas molecule ionization chamber 15 is sealed excluding the hole 27of the extraction electrode 24 and the gas supply piping 25. The gassupplied into the gas molecule ionization chamber through the gas supplypiping 25 does not leak from the region other than the hole 27 of theextraction electrode 27 and the gas supply piping 25. The interior ofthe gas molecule ionization chamber can be held at high air tightnessand sealability by having the diameter of the hole 27 of the extractionelectrode 24 sufficiently small. The diameter of the hole 27 of theextraction electrode 24 is smaller than or equal to 0.2 mm Thus, whenthe ionized gas is supplied to the gas ionization chamber 15 from thegas supply tube 25, the gas pressure of the gas ionization chamber 15becomes greater than the gas pressure of the vacuum chamber by at leastone figure. The proportion of the ion beam which collides with the gasin vacuum to be neutralized is thus reduced, and the ion beam of largecurrent can be generated.

The resistive heater 30 is used to perform degassing process on theextraction electrode 24, the side wall 28, and the like. The extractionelectrode 24, the side wall 28, and the like are degassed by heating.The resistive heater 30 is arranged on the outer side of the gasmolecule ionization chamber 15. Therefore, even if the resistive heateritself is degasified, this is carried out outside the gas moleculeionization chamber, and hence the interior of the gas moleculeionization chamber is at high vacuum.

In the present example, the resistive heater is used for the degassingprocess, but instead, the heating lamp may be used. The heating lamp cansimplify the peripheral structure of the extraction electrode as it canheat the extraction electrode 24 in a non-contact manner. Furthermore,since high voltage does not need to be applied in the heating lamp, thestructure of the heating lamp power supply is simple. Furthermore,instead of using the resistive heater, inactive gas of high temperaturemay be supplied through the gas supply piping 25 to heat the extractionelectrode, the side wall, and the like and perform the degassingprocess. In such a case, the gas heating mechanism can be at groundpotential. Furthermore, the peripheral structure of the extractionelectrode becomes simple, and wirings and power supplies areunnecessary.

The sample chamber 3 and the sample chamber vacuum exhaust pump 13 areheated up to about 200° C. by the resistive heater attached to thesample chamber 3 and the sample chamber vacuum exhaust pump 13 so thatthe degree of vacuum of the sample chamber 3 is smaller than or equal to10⁻⁷ Pa at maximum. Thus, contamination is avoided from attaching to thesurface of the sample when the sample is irradiated with the ion beam,and the surface of the sample can be satisfactorily observed. In theprior art, the observation of the sample surface was difficult as thegrowth of deposition by contamination is fast when the surface of thesample is irradiated with a beam of helium ion or hydrogen ion. Thesample chamber 3 and the sample chamber vacuum exhaust pump 13 are thusheating processed in the vacuum state to have the residual gas ofhydrocarbon system in vacuum of the sample chamber 3 to a microscopicamount. The outermost surface of the sample then can be observed at highresolution.

The operation of the gas field ion source of the present example willnow be described. The inside of the vacuum chamber is vacuum exhaustedby the ion source vacuum exhaust pump 12. The degassing process of theextraction electrode 24, the side wall 28, and the top plate 29 iscarried out by the resistive heater 30. In other words, the extractionelectrode 24, the side wall 28, and the top plate 29 are degassed byheating. Another resistive heater may be arranged on the outer side ofthe vacuum chamber to heat the vacuum chamber. The degree of vacuum inthe vacuum chamber thereby increases and the concentration of theresidual gas lowers. The time stability of the ion release current canbe enhanced by such operation.

After the degassing process is finished, the heating by the resistiveheater 30 is stopped and the refrigerator is operated after elapse of asufficient time. The emitter tip 21, the extraction electrode 24, theshield reducing the thermal radiation 58, and the like are therebycooled. The ionized gas is then introduced into the gas moleculeionization chamber 15 by the gas supply piping 25. The ionized gas ishelium or hydrogen, where description will be made herein with helium.As described above, the interior of the gas molecule ionization chamberhas high degree of vacuum. Therefore, the proportion of the ion beamgenerated by the emitter tip 21 which collides with the residual gas inthe gas molecule ionization chamber to be neutralized is reduced. Thus,the ion beam of large current can be generated. The number of the heliumgas molecules of high temperature which collides with the extractionelectrode is also reduced. The cooling temperature of the emitter tipand the extraction electrode thus can be lowered. Therefore, the samplecan be irradiated with the ion beam of large current.

The voltage is then applied between the emitter tip 21 and theextraction electrode 24. An intense electric field is formed at thedistal end of the emitter tip. Most of the helium supplied from the gassupply piping 25 is pulled to the emitter tip surface by the strongelectric field. The helium reaches the vicinity of the distal end of theemitter tip where the electric field is the strongest. The helium isthen field-ionized and the helium ion beam is generated. The helium ionbeam is guided to the ion beam irradiation system through the hole 27 ofthe extraction electrode 24.

The structure and the manufacturing method of the emitter tip 21 willnow be described. First, a tungsten wire having a diameter of about 100to 400 μm and an axial direction of <111> is prepared and the distal endthereof is molded sharp. The emitter tip having a distal end with acurvature radius of few 10 nm is thereby obtained. Platinum is thenvacuum deposited to the distal end of the emitter tip in a differentvacuum chamber. The platinum atoms are moved to the distal end of theemitter tip under high temperature heating. A pyramid structure ofnanometer order is thereby formed by the platinum atoms. This is calleda nano-pyramid. The nano-pyramid typically has one atom at the distalend, a layer of three or six atoms thereunder, and a layer of ten ormore atoms further thereunder.

In the present example, a thin wire of tungsten is used, but a thin wireof molybdenum may be used. The covering of platinum is used in thepresent example, but a covering of iridium, rhenium, osmium, palladium,rhodium, and the like may be used.

When using helium for the ionized gas, it is important that theevaporation intensity of the metal is greater than the electric fieldintensity at which the helium ionizes. Therefore, the coverage ofplatinum, rhenium, osmium, and iridium is suitable. When using hydrogenfor the ionized gas, the coverage of platinum, rhenium, osmium,palladium, rhodium, and iridium is suitable. The formation of thecoverage of such metals may be carried out through vacuum depositionmethod but may also be carried out by plating in a solution.

Other methods of forming the nano-pyramid at the distal end of theemitter tip include field evaporation in vacuum, ion beam irradiation,and the like. The tungsten atom or the molybdenum atom nano-pyramid canbe formed at the distal end of the tungsten wire or the molybdenum wireby such method. For instance, if the tungsten wire of <111> is used, thedistal end has a characteristic of being configured with three tungstenatoms.

As described above, the characteristic of the emitter tip 21 of the gasfield ion source according to the present invention is the nano-pyramid.The helium ion can be generated in the vicinity of one atom at thedistal end of the emitter tip by adjusting the electric field intensityformed at the distal end of the emitter tip 21. Therefore, the regionwhere the ion is released, that is, the ion light source is a verynarrow region of smaller than or equal to a nanometer. Therefore, thebeam diameter can be made to smaller than or equal to 1 nm by generatingthe ion from a very limited region. The current value per unit area andunit solid angle of the ion source thus becomes large. This is animportant property in obtaining the ion beam of microscopic diameter andlarge current on the sample.

In particular, when platinum is vapor deposited on the tungsten, thenano-pyramid structure in which one atom exists at the distal end isstably formed. In this case, the helium ion generation area isconcentrated at the vicinity of the one atom at the distal end. If threeatoms exist at the distal end of the tungsten <111>, the helium iongeneration area is dispersed at the vicinity of three atoms. Therefore,the current released from the unit area or the unit solid angle becomesgreater in the ion source having a nano-pyramid structure of platinum inwhich the helium gas is supplied in a concentrated manner to one atom.In other words, the emitter tip in which platinum is vapor deposited onthe tungsten is suitable in reducing the beam diameter on the sample ofthe ion microscope or in increasing the current. When the nano-pyramidhaving one atom at the distal end is formed using rhenium, osmium,iridium, palladium, rhodium, and the like, the current released from theunit area or the unit solid angle can be similarly increased, the beamdiameter on the sample of the ion microscope can be reduced, and thecurrent can be increased.

As described above, the position and the angle of the emitter tip areadjusted while observing the ion emission pattern in the observationmethod of the ion emission pattern, but the ion extraction voltage maybe adjusted and then the ion beam trajectory or the aperture positionmay be adjusted so that the ion beam passes through the aperture afterthe ion emission pattern becomes one from one atom of the tip.

The characteristic of the ion source herein is that the ion releasedfrom the vicinity of one atom at the distal end of the nano-pyramid isused. In other words, the region the ion is released is narrow, and theion light source is small or smaller than or equal to nanometer. Thus,the properties of the ion source can be exhibited to a maximum extent ifthe ion light source is focused on the sample at the same magnificationor the reduction rate is increased to about one half. In theconventional gallium liquid metal ion source, the dimension of the ionlight source is estimated to be about 50 nm Therefore, the reductionrate needs to be smaller than or equal to 1/10 in order to realize thebeam diameter of 5 nm on the sample. In this case, the vibration of theemitter tip of the ion source is reduced to smaller than or equal to onetenth on the sample. For instance, even if the emitter tip is vibratingby 10 nm, the vibration of the beam spot on the sample is smaller thanor equal to 1 nm Therefore, the influence of the vibration of theemitter tip with respect to the beam diameter of 5 nm is very small. Inthe present example, the reduction rate is small and is about 1 to ½.Therefore, the vibration of 10 nm at the emitter tip becomes thevibration of 5 nm on the sample, whereby the vibration of the samplewith respect to the beam diameter is large.

According to the present invention, the vibration proofing mechanism isarranged, as shown in FIG. 1. In other words, the vibration of therefrigerator 40 and the compressor 16 is less likely to be transmittedto the gas field ion source 1, the ion beam irradiation system column 2,and the sample chamber 3 by the vibration proofing mechanism 19. Thevibration of the compressor 16 is less likely to be transmitted to thepot 43 and the sample stage 10. Therefore, according to the presentinvention, a high resolution observation of the sample surface can berealized by generating an ion beam of small diameter. Furthermore, sincethe proportion the ion beam collides with the gas in vacuum andneutralizes is small as the air tightness of the gas molecule ionizationchamber is high in the ion source and the degree of vacuum is high onthe outer side of the gas molecule ionization chamber, an effect in thatthe sample can be irradiated with an ion beam of large current can beobtained. The effects in that the number the helium gas molecule of hightemperature collides with the extraction electrode reduces, the coolingtemperature of the emitter tip and the extraction electrode can belowered, and the sample can be irradiated with the ion beam of largecurrent are obtained.

The distance between the distal end of the objective lens 8 and thesurface of the sample 9 is referred to as a work distance. In thepresent ion beam device, the resolution becomes smaller than 0.5 mm ifthe work distance is smaller than 2 mm thereby realizingsuper-resolution. In the prior art, there was a possibility ofinhibiting the normal operation when the sputter particles from thesample contaminate the objective lens since ions such as gallium wasused. Such possibility is low and super-high resolution is realized inthe ion microscope according to the present invention.

If the nano-pyramid is damaged by unpredicted discharge phenomenon andthe like, the emitter tip is heated for about 30 minutes (about 1000°C.). The nano-pyramid then can be reproduced. In other words, theemitter tip can be easily repaired. A practical ion microscope thus canbe realized.

An inclination structure of the emitter tip of the gas field ion sourceof the present invention will be described with reference to FIG. 6A andFIG. 6B. The filament mount 23 is fixed to the emitter base mount 64, sothat they both integrally displace. The gas ionization chamber barelycontacts the vacuum chamber. The extremely low temperature of theionization chamber is thus realized. The walls surrounding theionization chamber at least should barely contact the vacuum chamber.The center axis line 66 passing the emitter tip 21 and the emitter basemount 64 can be inclined with respect to a vertical line 65, that is,the center axis line of the gas molecule ionization chamber 15. FIG. 6Ashows a state in which the center axis line 66 passing the filamentmount 23 and the emitter base mount 64 is not inclined with respect tothe vertical line 65 (two lines overlap in the figure). FIG. 6B shows astate in which the center axis line 66 passing the filament mount 23 andthe emitter base mount 64 is inclined with respect to the vertical line65.

In the present example, the position of the emitter tip 21 is constanteven if the center axis line passing the filament mount 23 and theemitter base mount 64 is inclined. In other words, the center axis line66 passing the filament mount 23 and the emitter base mount 64 pivots onthe emitter tip 21 as a center axis. Therefore, the emitter tip 21rotates but does not displace in the transverse direction. The ion beamgenerated at the distal end of the emitter tip 21 passes through thehole 27 of the extraction electrode 24 even if the center axis linepassing the filament mount 23 and the emitter base mount 64 is inclined.The center axis line of the extraction electrode overlaps or is parallelto the vertical line 65, that is, the center axis line of the ionirradiation system. Therefore, the electric field between the extractionelectrode and the lens does not distort, and the focusing property ofthe ion beam enhances.

When the center axis line passing the filament mount 23 and the emitterbase mount 64 does not pivot on the emitter tip 21 as a center axis, theemitter base mount 64 is to be moved within the XY plane after theinclination of the emitter tip 21.

The characteristic of the present structure lies in that the emitter tip21 is connected to the extraction electrode 24 through the deformablebellows 62 and the insulating material 63. Thus, with the extractionelectrode as a fixed structure, the emitter tip 21 is movable and can beinclined at the same time, and the helium does not leak other than tothe small hole 27 of the extraction electrode and the gas supply piping25 while surrounding the periphery of the emitter tip. This is theresult of connecting the emitter tip 21 and the extraction electrode 24with the deformable bellows 62 in between, and an effect of enhancingthe air tightness of the gas molecule ionization chamber is obtained. Ametal bellows is used in the present example, but similar effect isobtained even by connecting with a deformable material such as rubber.The characteristic also lies in that the ionization chamber in which theemitter tip is substantially surrounded by the emitter base mount, theshape varying mechanism component, the extraction electrode, and thelike is deformable in the vacuum chamber. The characteristic also liesin that the ionization chamber substantially does not contact the vacuumchamber of room temperature. Thus, the focusing property of the ion beamenhances, the sealability of the gas molecule ionization chamberenhances, and the high gas pressure of the gas molecule ionizationchamber can be realized.

When the center axis line passing the filament mount 23 and the emitterbase mount 64 is inclined, the displacement amount of the emitter basemount 64 is greater than the displacement amount of the filament mount23. The diameter of the bellows 61 connected to the emitter base mount64 is greater than the diameter of the bellows 62 connected to thefilament mount 23. Therefore, the bellows 61 is deformable so as to beable to absorb the displacement of the emitter base mount 64. Thebellows 62 is deformable so as to be able to absorb the displacement ofthe filament mount 23.

According to the gas field ion source of the present invention, thevibration from the cooling mechanism is less likely to be transmitted tothe emitter tip thereby enabling high resolution observation.

Furthermore, according to the gas field ion source of the presentinvention, the sealability of the gas molecule ionization enhances andthe high gas pressure of the gas molecule ionization chamber can berealized by making the hole 27 of the extraction electrode 24sufficiently small. Thus, the ion of large current can be released.

According to the gas field ion source of the present invention, theemitter can be made to an extremely low temperature since the heattransmission path from the cooling mechanism 4 to the emitter tip 21 isarranged. Thus, the ion beam of large current is obtained. Furthermore,according to the gas field ion source of the present invention, the axisadjustment of the emitter tip can be facilitated and larger current ofthe ion can be realized by having the extraction electrode as a fixedstructure and the emitter tip as a movable structure, and connecting theemitter tip and the extraction electrode with a deformable raw materialin between.

A second example of the ion microscope according to the presentinvention will be described with reference to FIG. 7. Comparing the ionmicroscope of the present example with the first example shown in FIG.1, a vibration free leg 102 is arranged in place of the device mount 17and the vibration proofing mechanism 19, and a surface plate 101 isarranged in place of the base plate 18 in the ion microscope of thepresent example. The surface plate 101 is formed by cast metal or stonematerial. The vibration free leg 102 may be configured by a vibrationproofing rubber, a spring, a damper, or a combination thereof.

The gas field ion source 1, the column 2, and the sample chamber 3 aresupported by the surface plate 101.

In the present example, a cooling mechanism in which the pulse tuberefrigerator 40 and the helium gas pot 43 are combined is used for thecooling mechanism 4 of the gas field ion source 1. The center axis lineof the pulse type refrigerator is arranged parallel to the optical axis14A of the ion beam irradiation system passing the emitter tip 21 of theion microscope. Both the enhancement of the focusing property of the ionbeam and the enhancement of the refrigerating function are thusrealized.

Similar to the cooling mechanism shown in FIG. 3 and FIG. 4, the emittertip 21, the sapphire base 52, the copper stranded wire 54, the coolingconduction rod 53, and the pot 43 compose the heat transmission path inthe present example as well. Similarly, the extraction electrode 24, thesapphire base 55, the copper stranded wire 56, the cooling conductionrod 53, and the pot 43 compose the heat transmission path. The copperstranded wire 54, which is a heat transferring member, is not limited tocopper member as long as it is a soft member having high thermalconductivity and is less likely to transmit vibration, and may be silverstranded wire.

The cooling stage of the refrigerator is covered by the sealing-type pot43. The cooling stage contacts the helium gas of the thermal conductoraccommodated in the helium gas pot 43 but is distant from the helium gaspot 43. The vibration from the main body of the pulse type refrigeratoris not transmitted to the helium gas pot 43 through the cooling stage.

The supporting column 103 is supported by the floor 20. The refrigerator40 is supported by the supporting column 103. The vibration of therefrigerator 40 is transmitted to the floor 20 through the supportingcolumn 103. However, the vibration of the refrigerator 40 is barelytransmitted from the floor 20 to the surface plate 101 by the vibrationfree leg 102. Therefore, the vibration of the refrigerator 40 is barelytransmitted to the gas field ion source 1, the ion beam irradiationsystem column 2, and the sample chamber 3 through the floor 20 therebyenabling the high resolution observation by the ion beam microscope.

The vibration of the compressor 16 is transmitted to the floor 20.However, the vibration of the compressor 16 is barely transmitted fromthe floor 20 to the surface plate 101 by the vibration free leg 102.Therefore, the vibration of the compressor 16 is barely transmitted tothe gas field ion source 1, the ion beam irradiation system column 2,and the sample chamber 3 through the floor 20 thereby enabling the highresolution observation by the ion beam microscope.

The supporting column 104 is arranged on the surface plate 101. Similarto the cooling mechanism shown in FIG. 3, the helium gas pot 43 issupported by the supporting column 104 in the present example as well.The vibration free leg 102 is arranged between the surface plate 101 andthe floor 20. Thus, the vibration of the refrigerator 40 and thecompressor 16 is barely transmitted to the helium gas pot 43 through thesupporting column 104.

The pulse type refrigerator does not include a mechanical drive unitnear the cooling stage. Therefore, the vibration generated by thecooling mechanism of the present example is small. The conventional gasfield ion source and the ion microscope have a problem in that theresolution of the observation degrades by the vibration of therefrigerator. In the ion microscope of the present example, however,reduction in the mechanical vibration can be achieved. This allows highresolution observation.

In the first example and the second example described above, themechanical refrigerator is used for the cooling mechanism 4 of the gasfield ion source 1. However, the mechanical refrigerator essentiallygenerates mechanical vibration, which may be transmitted to the emittertip or the sample stage. In the ion microscope, the vibration of theemitter tip vibrates the irradiation point on the sample of the beamthereby degrading the microscope resolution. In the following example,the mechanical refrigerator is not used for the cooling mechanism 4.

A third example of the ion microscope according to the present inventionwill be described with reference to FIG. 8. Comparing the ion microscopeof the present example with the first example shown in FIG. 1, theconfiguration of the cooling mechanism 4 for the gas field ion source 1is different. The cooling mechanism 4 will be described here. Thecooling mechanism 4 of the present example includes a vacuum chamber 81and a cooling tank 82. The vacuum chamber 81 is configured by the vacuumchamber, and the cooling tank 82 is accommodated therein. The vacuumchamber 81 and the cooling tank 82 do not contact. Therefore, thevibration and the heat are barely transmitted between the vacuum chamber81 and the cooling tank 82.

The cooling tank 82 includes a vacuum exhaust port 83. The vacuumexhaust port 83 is connected to a vacuum pump (not shown). A coolingconduction rod 53 made of copper similar to the first example shown inFIG. 3 is connected to the cooling tank 82. Similar to the coolingmechanism shown in FIG. 3 and FIG. 4, the emitter tip 21, the sapphirebase 52, the copper stranded wire 54, the cooling conduction rod 53, andthe cooling tank 82 compose the heat transmission path in the presentexample as well. Similarly, the extraction electrode 24, the sapphirebase 55, the copper stranded wire 56, the cooling conduction rod 53, andthe cooling tank compose the heat transmission path. The copper strandedwire 54, which is a heat transferring member, is not limited to coppermember as long as it is a soft member having high thermal conductivityand is less likely to transmit vibration, and may be silver strandedwire.

First, liquid nitrogen is introduced into the cooling tank 82, and theinterior of the cooling tank is vacuum exhausted through the vacuumexhaust port 83. The temperature of the liquid nitrogen thereby lowers.The liquid nitrogen solidifies and becomes solid nitrogen 84. Thesolidifying temperature in vacuum of the liquid nitrogen is about 51 K.

In the present example, after the liquid nitrogen is completelysolidified, the vacuum pump connected to the vacuum exhaust port 83 isstopped and the ion beam is generated by the emitter tip 21. Themechanical vibration of the vacuum pump is not generated when the vacuumpump is stopped. Thus, the ion emitter does not vibrate.

Heat is transmitted through the emitter tip 21 and the heat transmissionpath between the extraction electrode 24 and the cooling tank 82 duringthe generation of the ion beam. The solid nitrogen in the cooling tank82 thus sublimates or melts. In the present example, latent heat such assublimation heat and melting heat of the solid nitrogen can be used tocool the emitter tip 21 and the extraction electrode 24.

The vacuum pump connected to the vacuum exhaust port 83 is operated tovacuum exhaust the interior of the cooling tank 82 before all of thesolid nitrogen starts to liquefy and boil. The temperature of the liquidnitrogen thus lowers and the liquid nitrogen solidifies. After all theliquid nitrogen solidifies, the vacuum pump connected to the vacuumexhaust port 83 is again stopped. This is repeated so that thetemperature of the nitrogen in the cooling tank 82 can be constantlymaintained around the melting point of the nitrogen. The temperature ofthe nitrogen in the cooling tank 82 is always a lower temperature thanthe boiling point. Therefore, the vibration caused by the boiling of theliquid nitrogen does not occur. The cooling mechanism of the presentexample thus does not generate the mechanical vibration. This allowshigh resolution observation.

In the present example, the temperature of the nitrogen in the coolingtank 82 is measured to control the operation of the vacuum pumpconnected to the vacuum exhaust port 83. For instance, the operation ofthe vacuum pump connected to the vacuum exhaust port 83 is started whenthe temperature of the nitrogen reaches a predetermined temperaturehigher than the melting point. The operation of the vacuum pumpconnected to the vacuum exhaust port 83 is stopped when the temperatureof the nitrogen reaches a predetermined temperature lower than themelting point. The degree of vacuum may be measured instead of thetemperature of the nitrogen in the cooling tank 82 to control theoperation of the vacuum pump connected to the vacuum exhaust port 83.

In the present example, the liquid nitrogen in the cooling tank 82 iscooled by vacuum exhausting the interior of the cooling tank 82.However, this causes the nitrogen of gas phase to be exhausted and thenitrogen reduces with time. The solid nitrogen in the cooling tank 82may be cooled using the refrigerator. The reduction of nitrogen then canbe prevented. The generation of the ion beam by the gas field ion source1 is preferably stopped during the operation of the refrigerator. Inother words, according to the ion source of the present example, an ionmicroscope in which the reduction in the mechanical vibration isrealized and high resolution observation can be carried out is proposed.

The base plate 18 is arranged on the device mount 17 arranged on thefloor 20 by way of the vibration proofing mechanism 19. The gas fieldion source 1, the column 2, and the sample chamber 3 are supported bythe base plate 18.

The supporting column 85 is arranged on the device mount 17. The vacuumexhaust port 83 of the cooling tank 82 is supported by the supportingcolumn 85. The supporting column 85 and the vacuum chamber 81 areconnected by the bellows 86. The supporting column 87 is arranged on thebase plate 18. The vacuum chamber 81 is supported by the supportingcolumn 87, and at the same time, is suspended by the supporting column85 through the bellows 86.

The bellows 86 reduces the transmission of high frequency vibration.Therefore, the vibration from the floor 20 is reduced by the bellowseven if transmitted to the supporting column 85 through the device mount17. Therefore, the vibration from the floor 20 is barely transmitted tothe vacuum chamber 81 through the supporting column 85. The vibrationfrom the floor 20 is transmitted to the device mount 17. However, thevibration from the floor 20 is barely transmitted to the base plate 18by the vibration proofing mechanism 19. Therefore, the vibration fromthe floor 20 is barely transmitted to the vacuum chamber 81 through thesupporting column 87.

Therefore, according to the present example, the vibration from thefloor 20 is not transmitted to the vacuum chamber 81 and the coolingtank 82. The vibration from the floor 20 is thus not transmitted to thegas field ion source 1, the ion beam irradiation system column 2, andthe sample chamber 3 through the cooling mechanism 4.

In the prior art, an example that takes into consideration the vibrationof the tank for accommodating the liquid nitrogen is known. However,sufficient review is not made on the transmission of the vibration ofthe tank to the vacuum chamber thereby affecting the ion beam. Accordingto the present invention, the vibration of the cooling tank 82 is lesslikely to be transmitted to the vacuum chamber 81. The ion beammicroscope of high resolution is provided since the vibration from thefloor 20 through the vacuum chamber 81 and the cooling tank 82 isreduced.

The nitrogen is filled in the cooling tank 82 in the present example,but neon, oxygen, argon, methane, hydrogen and the like may be usedother than nitrogen. In particular, if solid neon is used, a lowtemperature suitable for obtaining larger current of the helium or thehydrogen ion beam can be achieved.

A fourth example of the ion microscope according to the presentinvention will be described with reference to FIG. 9. Comparing the ionmicroscope of the present example with the first example shown in FIG.1, the configuration of the cooling mechanism 4 for the gas field ionsource 1 is different. The cooling mechanism 4 will be described here.The cooling mechanism 4 of the present example is a helium circulatingtype.

The cooling mechanism 4 of the present example cools the helium gas,which is a cooling medium, using a GM refrigerator 401 and heatexchangers 402, 405, 409, 410, 412, 414, and circulates the same with acompressor unit 400. The helium gas having a temperature of 300 K atnormal temperature of 0.9 Mpa pressurized with the compressor unit(compressor) 400 flows into the heat exchanger 402 through a piping 403,and exchanges heat with the returning helium gas of low temperature, tobe described later, to be cooled to a temperature of about 60 K. Thecooled helium gas is transferred through the piping 403 of a heatinsulated transfer tube 404, and then flows into the heat exchanger 405arranged near the gas field ion source 1. The thermal conductorthermally integrated to the heat exchanger 405 is cooled to thetemperature of about 65 K to cool the shield reducing the thermalradiation, and the like described above. The warmed helium gas flows outfrom the heat exchanger 405 and flows into the heat exchanger 409thermally integrated to the first cooling stage 408 of the GMrefrigerator 401 through a piping 407. The helium gas is then cooled tothe temperature of about 50 K and flows into the heat exchanger 410. Thehelium gas then exchanges heat with the returning helium gas of lowtemperature to be described later to be cooled to the temperature ofabout 15 K, and thereafter, flows into the heat exchanger 412 thermallyintegrated to the second cooling stage 411 of the GM refrigerator 401.The helium gas is then cooled to the temperature of about 9 K,transferred through the piping 413 of the transfer tube 404, and flowsinto the heat exchanger 414 arranged near the gas field ion source 1.The helium gas cools the cooling conduction rod 53 of satisfactorythermal conductor thermally connected to the heat exchanger 414 to thetemperature of about 10 K. The helium gas warmed by the heat exchanger414 sequentially flows into the heat exchangers 410, 402 through thepiping 415. The helium gas then exchanges heat with the helium gasdescribed above and becomes substantially a normal temperature or atemperature of about 275 K. The helium gas is collected by thecompressor unit 400 through the piping 415. The low temperature portionis accommodated in a vacuum heat insulating container 416, and isconnected in a heat insulating manner (not shown) to the transfer tube404. Furthermore, although not shown, the low temperature portionprevents heat penetration due to radiation heat from the roomtemperature portion by the shield plate reducing the thermal radiation,the stacked layer heat insulating material, and the like in the vacuumheat insulating container 416.

The transfer tube 404 is securely fixed and supported on the floor 20 ora supporting body 417 installed on the floor 20. Although not shown, thepiping 403, 407, 413, 415 are fixed and supported by a plastic heatinsulating body with glass fiber or a heat insulating material havinglow thermal conductivity at inside the transfer tube 404. The piping403, 407, 413, 415 are also fixed and supported on the floor 20.

The transfer tube 404 is also securely fixed and supported by asupporting body 418 installed on the base plate 18 at near the gas fieldion source 1. Similarly, although not shown, the piping 403, 407, 413,415 are fixed and supported by a plastic heat insulating body with glassfiber or a heat insulating material having low thermal conductivity atinside of the transfer tube 404. The piping 403, 407, 413, 415 are alsofixed and supported on the base plate 18.

In other words, the cooling mechanism is a coldness generation means forgenerating coldness by expanding a first high pressure gas generated bythe compressor unit 16, and a cooling mechanism for cooling a body to becooled with helium gas or a second moving cooling medium cooled with thecoldness of the coldness generation means and circulated with thecompressor unit 400.

The cooling conduction rod 53 is connected to the emitter tip 21 throughthe deformable cooper stranded wire 54 and the sapphire base. Thecooling of the emitter tip 21 is thereby realized. In the presentexample, the GM refrigerator becomes a factor for vibrating the floor,but the gas field ion source 1, the ion beam irradiation system column2, the vacuum sample chamber 3 and the like are installed isolated fromthe GM refrigerator. Furthermore, the piping 403, 407, 413, 415 coupledto the heat exchangers 405, 414 installed in the vicinity of the gasfield ion source 1 are securely fixed and supported on the floor 20 orthe base 18 that barely vibrates. The piping thus do not vibrate.Furthermore, the gas field ion source 1, the ion beam irradiation systemcolumn 2, the vacuum sample chamber 3, and the like are vibrationinsulated from the floor and thus are systems in which the transmissionof mechanical vibration is extremely small.

In other words, according to the gas field ion source of the presentexample, a gas field ion source and an ion microscope in which themechanical vibration can be reduced and high resolution observation canbe carried out.

Furthermore, in the present example as well, the vibration proofingmechanism may be arranged on the base plate 18 that supports the gasfield ion source 1, the ion beam irradiation system column 2, and thesample chamber 3. The reduction and transmission of the mechanicalvibration are thereby prevented, enabling high resolution observation.

The inventors of the present application found that the sound of thecompressor 16 or 400 vibrates the gas field ion source 1 and degradesthe resolution thereof. Thus, a cover 419 for spatially separating thecompressor and the gas field ion source is arranged in the presentexample. The influence of the vibration caused by the sound of thecompressor thus can be reduced. High resolution observation also can becarried out. In the examples shown in FIG. 1, FIG. 7, and FIG. 8 aswell, the cover may be arranged to reduce the influence of the vibrationcaused by the sound of the compressor.

In the case of the present example, the second helium gas is circulatedusing the compressor unit (compressor) 400. However, although not shown,the piping 111, 112 of the helium compressor 16 and the piping 403, 414may be communicated through a flow rate adjustment valve, respectively.Some of the helium gas from the helium compressor 16 thus can besupplied into the piping 409 as a second helium gas, that is, thecirculating helium gas, and the gas can be collected to the heliumcompressor 16 from the piping 416. Similar effect thus can be obtained.

The GM refrigerator 401 is used in the present example, but instead, apulse tube refrigerator or a sterling refrigerator may be used.Furthermore, the refrigerator includes two cooling stages in the presentexample, but may include a single cooling stage, where the number ofcooling stages is not particularly limited. For example, a smallsterling refrigerator having one cooling stage may be used. A compactand low-cost ion beam device thus can be realized with a heliumcirculating refrigerator in which the lowest cooling temperature is 50K. In such a case, neon gas or hydrogen may be used in place of thehelium gas.

A fifth example of the ion microscope according to the present inventionwill be described with reference to FIG. 10A and FIG. 10B. The structureof the gas molecule ionization chamber of the gas field ion source willnow be described. The present example has characteristics in the vacuumexhaust mechanism of the gas molecule ionization chamber. In the gasmolecule ionization chamber 15 of the present example, an opening isformed in the top plate 29, and an open/close valve is attached to theopening 31. The open/close valve includes a lid member 32 for closingthe opening 31 and an operation rod 33 attached to the lid member 32.The operation rod 33 passes through the shield reducing the thermalradiation 58 or the vacuum chamber 68 and extends to the outside of thevacuum chamber. The operation rod 33 is configured to be operable at theouter side of the vacuum chamber.

FIG. 10A shows a state in which the lid member 32 is separated from theopening 31. In this case, the open/close valve is isolated from a wallstructure of the gas molecule ionization chamber 15, and can prevent theheat from flowing into the gas molecule ionization chamber 15 throughthe open/close valve. In other words, it is suitable for lowering thetemperature of the gas molecule ionization chamber. FIG. 10B shows astate in which the opening 31 is closed by the lid member 32. In thiscase, the gas molecule ionization chamber 15 is sealed excluding the gassupply piping 25 and the hole 27.

The operation of the gas field ion source of the present example willnow be described. First, as shown in FIG. 10A, coarse exhaust is carriedout with the opening 31 of the gas molecule ionization chamber 15opened. The emitter tip 21 prepared in advance is attached, and thevacuum chamber is exhausted by the vacuum pump 12. The conductance withrespect to the vacuum exhaust system of the gas molecule ionizationchamber 15 is relatively large when the opening 31 is opened. Therefore,the coarse exhaust of the gas molecule ionization chamber 15 iscompleted in a short period of time.

Therefore, according to the present example, the conductance in time ofcoarse vacuum can be increased even if the dimension of the hole 27 ofthe extraction electrode 24 is reduced by forming the opening 31 in thegas molecule ionization chamber 15. The gas molecule ionization chamber15 can be sealed by reducing the dimension of the hole of the extractionelectrode. Thus, high vacuuming of the gas molecule ionization chamber15 can be realized, and the ion beam of large current is obtained.

The extraction electrode 24, the side wall 28, and the top plate 29 canbe degassed by heating with the resistive heater 30 on the outer side ofthe side wall of the gas molecule ionization chamber 15. In the presentexample as well, another resistive heater for degassing process may bearranged on the outer side of the vacuum chamber. The residual gasconcentration lowers and the degree of vacuum enhances by the degassingprocess of the vacuum chamber. The time stability of the ion releasecurrent can be enhanced by the degassing process. The opening 31 of thegas molecule ionization chamber 15 is then closed, and the helium issupplied from the gas supply piping 25, as shown in FIG. 10B. Highvoltage is supplied to the emitter tip 21 to apply the extractionvoltage to the extraction electrode 24. The ion beam is generated fromthe distal end of the emitter tip 21.

In the present example, the resistive heater 30 is arranged on the outerside of the gas molecule ionization chamber 15. Thus, degassing of theresistive heater itself is carried out outside the gas moleculeionization chamber 15. The interior of the gas molecule ionizationchamber 15 thus becomes higher vacuum.

A sixth example of the ion microscope according to the present inventionwill be described with reference to FIG. 11A and FIG. 11B. The structureof the gas molecule ionization chamber of the gas field ion source willbe described below. The present example has characteristics in thewiring structure of the gas molecule ionization chamber. The gas fieldion source includes a heating power supply 134 for heating the emittertip 21, a high voltage power supply 135 for supplying an acceleratingvoltage for accelerating ions to the emitter tip 21, an extraction powersupply 141 for supplying an extraction voltage for extracting ions tothe extraction electrode 24, and a heating power supply 142 for heatingthe resistive heater 30.

The heating power supplies 134, 142 may be 10V, the high voltage powersupply 135 may be 30 kV, and the extraction power supply 141 may be 3kV.

As shown in FIG. 11A, a filament 22 and the high voltage power supply135 are connected by a thick wire 133 made of copper and a thin wire 136made of stainless steel. The filament 22 and the heating power supply134 are connected by the thick wire 133 made of copper. The resistiveheater 30 and the heating power supply 142 are connected by a thick wire138 made of copper. The extraction electrode 24 and the resistive heater30 have the same potential.

As shown in FIG. 11B, the filament 22 and the high voltage power supply135 are connected by the thin wire 136 made of stainless steel. Theextraction electrode 24 and the extraction power supply 141 areconnected by the thin wire 139 made of stainless steel.

A disconnecting mechanism 137 is arranged on the thick wire 133 made ofcopper. The disconnecting mechanism 137 includes a movable mechanism,and is configured to move between two positions, a disconnectingposition of disconnecting the thick wire 133 made of copper from thefilament 22 and a connecting position of connecting the thick wire 133made of copper to the filament 22. A disconnecting mechanism 140 isarranged on the thick wire 138 made of copper. The disconnectingmechanism 140 includes a movable mechanism, and is configured to movebetween two positions, a disconnecting position of disconnecting thethick wire 138 made of copper from the resistive heater 30 and aconnecting position of connecting the thick wire 138 made of copper tothe resistive heater 30. FIG. 11A shows a state in which thedisconnecting mechanisms 137, 140 are both at the connecting position,and FIG. 11B shows a state in which the disconnecting mechanisms 137,140 are both at the disconnecting position. When the disconnectingmechanisms 137, 140 are both at the disconnecting position, the heat isprevented from flowing into the filament 22 and the extraction powersupply 141 through the thick wires 133, 138 made of copper,respectively. The disconnecting mechanisms 137, 140 are operable fromoutside the vacuum chamber.

In the present example as well, an open/close valve for opening andclosing the gas molecule ionization chamber 15 is attached. Theopen/close valve includes a lid member 34. FIG. 11A shows a state inwhich the lid member 34 is opened, and FIG. 11B shows a state in whichthe lid member 34 is closed.

The operation of the gas field ion source of the present example will bedescribed. First, as shown in FIG. 11A, coarse exhaust is carried outwith the lid member 34 of the gas molecule ionization chamber 15 opened.The coarse exhaust of the gas molecule ionization chamber 15 iscompleted in a short period of time since the lid member 34 of the gasmolecule ionization chamber 15 is opened.

The extraction electrode 24, the side wall 28, and the top plate 29 areperformed with the degassing process by being heated by the resistiveheater 30 on the outer side of the side wall of the gas moleculeionization chamber 15. After the degassing process is completed, thedisconnecting mechanism 140 is moved to the disconnecting position, asshown in FIG. 11B. The heat is thus prevented from flowing into the gasmolecule ionization chamber 15 through the thick wire 138 made ofcopper.

The lid member 34 of the gas molecule ionization chamber 15 is thenclosed, and the helium is supplied from the gas supply piping 25. Highvoltage is then supplied to the emitter tip 21 to apply the extractionvoltage to the extraction electrode 24. After the ion beam is generatedfrom the distal end of the emitter tip 21, the disconnecting mechanism137 is moved to the disconnecting position. The heat is thus preventedfrom flowing into the gas molecule ionization chamber 15 through thethick wire 133 made of copper. When the disconnecting mechanism 137 isat the disconnecting position, the accelerating voltage from the highvoltage power supply 135 is not applied to the filament 22 through thethick wire 133 made of copper but is applied to the filament 22 throughthe thin wire 136 made of stainless steel. When the disconnectingmechanism 140 is at the disconnecting position, the extraction voltagefrom the extraction power supply 141 is not applied to the extractionpower supply 141 through the thick wire 138 made of copper but isapplied to the filament 22 through the thin wire 139 made of stainlesssteel. The filament 22 and the extraction power supply 141 are connectedon a steady basis to the thin wires 136, 139 made of stainless steel.Therefore, there is a possibility the heat may flow into the gasmolecule ionization chamber 15 through the thin wires 136, 139 made ofstainless steel. However, the heat transferring amount through the thinwires 136, 139 made of stainless steel is sufficiently small since thethin wires 136, 139 made of stainless steel have sufficiently smallcross-sections.

According to the wiring structure of the present example, the flow ofheat from the copper wiring to the gas molecule ionization chamber 15can be avoided. Thus, the emitter tip and the extraction electrode canbe held at the desired temperatures. In other words, enhancement in theluminance of the ion source and larger current of the ion beam can beachieved. Furthermore, high resolution observation can be carried out.

According to the present example, the conductance in time of coarsevacuuming can be increased even if the dimension of the hole of theextraction electrode is reduced by arranging the lid member 34 on thegas molecule ionization chamber 15. The gas molecule ionization chamber15 can be sealed by reducing the dimension of the hole of the extractionelectrode. Thus, high vacuuming of the gas molecule ionization chamber15 can be realized, and the ion beam of large current is obtained.

The wiring structure described herein can be applied even in theexamples shown in FIG. 1, FIG. 7, and FIG. 8.

In the scanning ion microscope described above, a scanning ion image canbe obtained by scanning the ion beam with the ion beam scanningelectrode. In this case, however, the ion beam distorts since the ionbeam inclines when the ion beam passes the ion lens. Thus, the problemin that the beam diameter does not become small arises. The sample stagemay be scanning moved mechanically in two orthogonal directions insteadof scanning the ion beam. In this case, the scanning ion image can beobtained on the image display means of the calculation processing deviceby detecting the secondary particles released from the sample andluminance modulating the same. In other words, the high resolutionobservation of less than 0.5 nm of the sample surface can be realized.In this case, the distortion of the ion beam can be made relativelysmall since the ion beam can be held constantly in the same directionwith respect to the objective lens.

This can be realized using the sample stage in which the first andsecond stages are combined. The first stage is a four-axes movable stagethat can move a few centimeters, and can move in two perpendiculardirections (X, Y directions) in plane, move in the height direction (Zdirection), and incline (T direction). The second stage is a two-axesmovable stage that can move a few micrometers, and can move in twoperpendicular directions (X, Y directions) in plane.

For instance, the second stage by a piezoelectric element drive isarranged on the first stage of electric motor drive. The sample is movedusing the first stage in the case of searching the observation positionof the sample, and the like, and is finely moved using the second stagein the case of the high resolution observation. The ion microscopeenabling super-high resolution observation is thereby provided.

A seventh example of the ion microscope according to the presentinvention will now be described with reference to FIG. 12. The ionmicroscope of the present example adopts a refrigerator mechanism ofhelium circulating type used in the ion microscope of the fourth exampleshown in FIG. 9. The seventh example differs from the fourth example inthe sample stage. Here, the sample stage is a side entry type.

The side entry type sample stage 500 of the present example can beinserted to the ion beam device without opening the vacuum of the samplechamber 3. The vacuum does not need to be broken when taking out theside entry type sample stage 500. The side entry type sample stage 500has a structure of being mounted on a sample stage fine movementmechanism 501. The sample can be moved in X, Y perpendicular directionswith respect to the ion beam by the sample stage fine movement mechanism501. The side entry type sample stage 500 includes a circular columnportion 503, a grip portion 502 for operating the sample stage, and asample mounting portion 505. Furthermore, a microscopic projection 504that contacts the interior wall surface of the sample chamber isarranged at the distal end of the sample stage. In the present ion beamdevice, the sample stage is fixed by the microscopic projection 504.Thus, the vibration of the sample is reduced thereby enabling theobservation of super-high resolution. Conventionally, such side entrytype sample stage is not adopted in the ion beam device having theresolution performance of smaller than or equal to 1 nm. In particular,in order to exhibit the performance of the ion beam device to a maximumextent, the inventors focused on the relative position fluctuation ofthe emitter and the sample and found that the gas field ion source andthe sample chamber are to have a structure of small vibration and thatthe sample stage suitable for realizing such strong device structure isthe side entry type sample stage.

Although not shown, an electron gun for neutralizing the charge up ofthe sample of when the ion beam is irradiated, or a gas gun forsupplying reactive gas to the vicinity of the sample is sometimesarranged in the side entry type sample stage. In such a case as well, aneffect that the spatial interference with the sample stage can berelatively easily avoided is obtained in the side entry type samplestage. The distance, that is, the work distance between the sample andthe objective lens thus can be reduced. The super resolution is therebyrealized. The features of the ion beam device using the gas field sourceion source are also exhibited.

In the ion beam device according to the present invention describedabove, it was found that high resolution that is difficult even with thescanning electronic microscope of the prior art can be achieved. Inparticular, the ion beam device of super-high resolution of smaller thanor equal to 0.2 nm can be achieved by having the magnification at whichthe ions released from the emitter tip are projected on the sample to besmaller than 0.2, and the fluctuation with respect to time of therelative position of the emitter tip and the sample to be smaller thanor equal to 0.1 nm Large current is essentially obtained if themagnitude at which the ions released from the emitter tip are projectedon the sample is about 0.5 to 1, but cost is required for thecountermeasures of vibration. Thus, it is found that if the magnitude issmaller than or equal to 0.2 so that the vibration of the emitter isreduced on the sample and the current is increased by cooling theemitter temperature to lower than or equal to 50 K, large current can beobtained and the ion beam device of high resolution can be achieved.

The scanning ion microscope has been described above as an example ofthe ion beam device of the present invention. However, the ion beamdevice of the present invention is applicable not only to the scanningion microscope but also to the transmission ion microscope and the ionbeam processing device.

The vacuum pump 12 for vacuum exhausting the gas field ion source willnow be described. The vacuum pump 12 is suitably configured by acombination of a non-evaporative getter pump and an ion pump, acombination of a non-evaporative getter pump and a noble pump, or acombination of a non-evaporative getter pump and an excel pump. Asublimation pump may be used. It is found that the influence of thevibration of the vacuum pump 12 can be reduced and high resolutionobservation can be carried out using such pump. It is found that whenusing a turbo molecular pump for the vacuum pump 12, the vibration ofthe turbo molecular pump may inhibit the observation in time of thesample observation by the ion beam. However, it is recognized that highresolution observation can be carried out by stopping the turbomolecular pump in time of the sample observation by the ion beam even ifthe turbo molecular pump is attached to any one of the vacuum chambersof the ion beam device. In other words, although the main vacuum exhaustpump in time of the sample observation by the ion beam is configured bya combination of the non-evaporative getter pump and the ion beam, acombination of the non-evaporative getter pump and the noble pump, or acombination of the non-evaporative getter pump and the excel pump in thepresent invention, the object of the present invention is not obstructedeven with the configuration of attaching the turbo molecular pump.

The non-evaporative getter pump is a vacuum pump configured using analloy that gas adsorbs by activation through heating. When using heliumfor the ionized gas of the gas field ion source, the helium exists in arelatively large amount in the vacuum chamber. However, thenon-evaporative getter pump barely exhausts the helium. Thus, the gettersurface does not saturate with the adsorption gas molecules. Thus, theoperation time of the non-evaporative getter pump is sufficiently long.This is the advantage of when the helium ion microscope and thenon-evaporative getter pump are combined. An effect in that the ionrelease current stabilizes as the impurity gas in the vacuum chamberreduces is also obtained.

Although the non-evaporative getter pump exhausts the residual gas otherthan the helium at a large exhaust speed, the helium will still retainin the ion source. Thus, the degree of vacuum becomes insufficient andthe gas field ion source does not normally operate. The ion pump or thenoble pump in which the exhaust speed of an inactive gas is large isthus used in combination with the non-evaporative getter pump. Theexhaust speed is insufficient with only the ion pump or the noble pump.According to the present invention, a compact and low cost vacuum pump12 can be obtained by combining the non-evaporative getter pump and theion pump or the noble pump. A getter pump or a titanium sublimation pumpfor adsorbing the gas molecules with a metal film by heat evaporatingthe metal such as titanium to vacuum exhaust may be used in combinationfor the vacuum pump 12.

The performance of the ion microscope is not sufficiently obtained dueto lack of consideration on the mechanical vibration in the prior art,but the present invention provides a gas field ion source and an ionmicroscope in which the mechanical vibration is reduced and the highresolution observation is enabled.

The sample chamber vacuum exhaust pump 13 for vacuum exhausting thesample chamber 3 will now be described. The sample chamber vacuumexhaust pump 13 may be a getter pump, a titanium sublimation pump, anon-evaporative getter pump, an ion pump, a noble pump, an excel pump,or the like. It is found that the influence of the vibration of thesample chamber vacuum exhaust pump 13 can be reduced and the highresolution observation can be carried out using such pump.

The turbo molecular pump may be used for the sample chamber vacuumexhaust pump 13. However, cost is required to realize thevibration-alleviating structure of the device. Furthermore, it isrecognized that high resolution observation can be carried out bystopping the turbo molecular pump in time of the sample observation bythe ion beam even if the turbo molecular pump is attached to the samplechamber. In other words, the main vacuum exhaust pump in time of thesample observation by the ion beam is configured by a combination of thenon-evaporative getter pump and the ion beam, a combination of thenon-evaporative getter pump and the noble pump, or a combination of thenon-evaporative getter pump and the excel pump in the present invention.However, the object of the present invention is not obstructed even ifthe turbo molecular pump is attached in the device configuration to usefor coarse vacuuming from the atmosphere.

In the scanning electron microscope, the resolution of smaller than orequal to 0.5 can be relatively easily achieved using the turbo molecularpump. However, in the ion microscope using the gas field ion source, thereduction rate of the ion beam from the ion light source to the sampleis relatively large or about 1 to 0.5. The properties of the ion sourcethus can be exhibited to a maximum extent. However, since the vibrationof the ion emitter is reproduced on the sample without practically beingreduced, cautious countermeasures are necessary even in comparison withthe vibration countermeasures of the scanning electron microscope andthe like of the prior art.

In the prior art, consideration is made in that the vibration of thesample chamber vacuum exhaust pump influences the sample stage, butconsideration is not made in that the vibration of the sample chambervacuum exhaust pump also influences the ion emitter. The inventors ofthe present application thus found that the vibration of the samplechamber vacuum exhaust pump seriously influences the ion emitter. Theinventors of the present invention believed that it is good to use anon-vibrating vacuum pump such as the getter pump, the titaniumsublimation pump, the non-evaporative getter pump, the ion pump, thenoble pump, and the excel pump as the main pump for the sample chambervacuum exhaust pump. This reduces the vibration of the ion emitter andenables high resolution observation.

The compressor unit (compressor) of the gas of the refrigerator used inthe present example or the compressor unit (compressor) for circulatingthe helium has a possibility of being the sound source of noise. Thenoise may vibrate the ion microscope. Thus, according to the presentinvention, the noise generated by the compressor unit of gas isprevented from being transmitted to the outside by arranging the coveron the compressor unit (compressor) of gas. A sound shielding plate maybe arranged instead of the cover. The compressor unit (compressor) maybe installed in a different room. The vibration caused by sound thusreduces thereby enabling high resolution observation.

The non-evaporative getter material may be arranged in the gas moleculeionization chamber. High vacuuming of the gas molecule ionizationchamber and highly stable ion release are thereby achieved. Hydrogen maybe adsorbed to the non-evaporative getter material or hydrogen storingalloy, and then heated. The hydrogen thereby released is used as theionized gas, so that gas does not need to be supplied from the gassupply piping 25 and a compact and safe gas supplying mechanism can berealized.

The non-evaporative getter material may be arranged in the gas supplypiping 25. The impurity gas in the gas supplied through the gas supplypiping 25 reduces by the non-evaporative getter material. Thus, the ionrelease current stabilizes.

In the present invention, helium or hydrogen is used for the ionized gassupplied to the gas molecule ionization chamber 15 through the gassupply piping 25. However, neon, oxygen, argon, krypton, xenon, or thelike may be used for the ionized gas. In particular, when using neon,oxygen, argon, krypton, xenon, and the like, an effect in that thedevice for processing the sample or the device for analyzing the samplecan be provided is obtained.

When using inactive gas such as helium, neon, argon, krypton, or xenon,the non-evaporative getter material may be arranged in the gas supplypiping 25. Alternatively, a gas tank may be arranged in the middle ofthe gas supply piping 25, and the non-evaporative getter material may bearranged in the gas tank. The gas other than the ionized gas is therebyadsorbed and the inactive gas can be purified. The ion release currentthereby stabilizes.

A mass spectrometer may be arranged in the sample chamber 3. The massspectrometry of the secondary ion released from the sample is carriedout with the mass spectrometer. Alternatively, the Auger electronreleased from the sample may be energy analyzed. The element analysis ofthe sample is thereby facilitated, and the sample observation by the ionmicroscope and the element analysis can be carried out in one device.

In the ion microscope of the present invention, the electrons can beextracted from the emitter tip by applying a high negative voltage tothe emitter tip. The sample is irradiated with such electron beam todetect the X ray or the Auger electrons released from the sample. Theelement analysis of the sample is thereby facilitated, and the sampleobservation of super-high resolution by the ion microscope and theelement analysis can be carried out in one device.

Furthermore, in this case, the ion image and the element analysis imagehaving a resolution of smaller than or equal to 1 nm may be displayedside by side or overlapped. The sample surface thus can be suitablyperformed with characterization.

In this case, the electron beam can be focused to a microscopic beamdiameter at a large current thereby enabling a highly sensitive elementanalysis at high spatial resolution by using a compound lens in which amagnetic field lens and an electrostatic lens are combined to theobjective lens for focusing the electron beam.

Although the disturbance of the external magnetic field is not takeninto consideration in the conventional ion beam device, it was foundthat the magnetism can be shielded when focusing the ion beam to smallerthan 0.5 nm Thus, super-high resolution can be achieved by creating thegas field ion source and the ion beam irradiation system, as well as thevacuum chamber of the sample chamber with pure iron or permalloy.Moreover, a plate for shielding magnetism may be inserted in the vacuumchamber.

The inventors of the present application found that more accuratemeasurement can be made by measuring the structural dimension of thesemiconductor sample with the accelerating voltage of the ion beam atgreater than or equal to 50 kV. This is because the extent of breakingthe structure of the sample lowers and the dimension measurementaccuracy enhances when the sputtering yield of the sample by the ionbeam lowers. In particular, the sputtering yield lowers and the accuracyof the dimension measurement enhances when hydrogen is used for theionized gas.

Therefore, according to the present invention, an analyzer suitable formeasuring the structural dimension on the sample with the ion beam, anda length measurement device or an examination device using the ion beamcan be provided.

Furthermore, according to the present invention, accurate measurementcan be carried out compared to the measurement using the electron beamof the prior art since the focal length of the image obtained is deep.Furthermore, the amount the sample surface is scraped becomes small andaccurate measurement can be carried out if hydrogen, in particular, isused for the ionized gas.

According to the present invention, a length measurement device or anexamination device using an ion beam suited for measuring the structuraldimension on the sample is provided.

According to the present invention, a device and a cross-sectionobservation method for forming a cross-section by processing with theion beam and observing the cross-section with the ion microscope can beprovided in place of a device for forming a cross-section by processingthe sample with the ion beam and observing the cross-section with theelectron microscope.

According to the present invention, a device in which sample observationby the ion microscope, the sample observation by the electronmicroscope, and the element analysis can be performed with one device,an analyzer for observing and analyzing defects, foreign substances, andthe like, and an examination device can be provided.

The ion microscope realizes a super-high resolution observation.However, when the ion beam was conventionally used as the measurementdevice or the examination device of the structural dimension in themanufacturing process of the semiconductor sample, a review on theinfluence on manufacturing of the breakage of the surface of thesemiconductor sample for the ion beam irradiation as opposed to theelectron beam irradiation is not made. For instance, the proportion thesample alters is small when the energy of the ion beam is smaller than 1keV, whereby the accuracy of the dimension measurement enhances comparedto when the energy of the ion beam is 20 keV. An effect in the cost ofthe device also reduces is obtained in this case. If the acceleratingvoltage is greater than or equal to 50 kV, on the other hand, theobservation resolution can be lowered compared to when the acceleratingvoltage is low.

Furthermore, the inventors of the present application found that thethree-dimensional structure including the plane and the depth of thesample element can be measured in units of atoms when the sample isirradiated with the accelerating voltage of the ion beam at greater thanor equal to 200 kV and the beam diameter narrowed to smaller than orequal to 0.2 nm, and performing the energy analysis of the ionsRutherford back scattered from the sample. The three-dimensionalmeasurement in the order of atoms was difficult in the conventionalRutherford back scattering device as the ion beam diameter is large, butthis can be realized by applying the present invention.

The two-dimensional analysis of the sample element can be carried out byirradiating the sample with the accelerating voltage of the ion beam atgreater than or equal to 500 kV and the beam diameter narrowed tosmaller than or equal to 0.2 nm, and performing the energy analysis ofthe X ray released from the sample.

According to the present invention, the following gas field ion source,the ion microscope, and the ion beam device are disclosed.

(1) A gas field ion source, configured by a vacuum chamber, a vacuumexhaust mechanism, an emitter tip that composes a needle-shaped anodeand an extraction electrode that composes a cathode in the vacuumchamber, for supplying gas molecules to a vicinity of a distal end ofthe emitter tip and ionizing the gas molecules with an electric field atthe distal end of the emitter tip; wherein

a mount of the emitter tip and the extraction electrode are connectedincluding a shape changeable mechanism component, an ionization chamberin which the emitter tip is substantially surrounded by at least themount of the emitter tip, the extraction electrode, and the shapechangeable mechanism component is deformable in the vacuum chamber whilebarely contacting the vacuum chamber.

(2) The gas field ion source according to (1), wherein

a gas pressure of the ionization chamber is greater by greater than orequal to at least one digit than a gas pressure of the vacuum chamberwhen the gas molecule is supplied to the ionization chamber.

(3) The gas field ion source according to (1), wherein the mount of theemitter tip is connected to the vacuum chamber including a shapechangeable mechanism component different from the shape changeablemechanism component.

(4) The gas field ion source according to (1) to (3), wherein the shapechangeable mechanism component is a bellows.

(5) The gas field ion source according to (4), wherein a minimumdiameter of the bellows between the mount of the emitter tip and theextraction electrode is smaller than a maximum diameter of the bellowsbetween the mount of the emitter tip and the vacuum chamber.

(6) An ion beam device comprising an ion beam device main body includinga gas field ion source, configured by a vacuum chamber, a vacuum exhaustmechanism, an emitter tip that composes a needle-shaped anode and anextraction electrode that composes a cathode in the vacuum chamber, anda cooling mechanism of the emitter tip, for supplying gas molecules to avicinity of a distal end of the emitter tip and ionizing the gasmolecules with an electric field at the distal end of the emitter tip, alens system for focusing an ion beam extracted from the emitter tip, asample chamber incorporating a sample, and a secondary particle detectorfor detecting secondary particles released from the sample; a base plateto mount the ion beam device main body; and a mount for supporting thebase plate, wherein a vibration proofing mechanism is arranged betweenthe ion beam device main body and the base plate, the cooling mechanismis supported by a supporting mechanism fixed to a floor, on which theion beam device is installed, or an ion beam device mount, and avibration proofing mechanism is arranged between a refrigerator and thevacuum chamber.

(7) The ion beam device according to (6), wherein the cooling mechanismis a coldness generation means for generating coldness by expanding ahigh pressure gas generated in a compressor unit, and a refrigerator forcooling a stage with the coldness of the coldness generation means.

(8) The ion beam device according to (6), wherein the cooling mechanismis a coldness generation means for generating coldness by expanding afirst high pressure gas generated in a compressor unit, and a coolingmeans for cooling a body to be cooled with a gas cooled with thecoldness of the coldness generation means.

(9) The ion beam device according to (6), wherein the cooling mechanismis a coldness generation means for generating coldness by expanding afirst high pressure gas generated in a compressor unit, and a coolingmeans for cooling a body to be cooled with a second high pressure gascooled with the coldness of the coldness generation means.

(10) The ion beam device according to (6), wherein the vibrationproofing mechanism between the refrigerator and the vacuum chamber atleast includes a mechanism for inhibiting transmission of vibration withhelium or neon gas.

(11) The ion beam device according to (6), wherein at least a shapechangeable mechanism component exists between a cooling stage of thecooling mechanism and the emitter tip.

(12) The ion beam device according to (6), wherein the cooling mechanismis a mechanism for holding a cooling agent in which a cooling mediumgas, which is in a gas state under normal temperature and atmospherepressure, is in a liquid or solid state by the vacuum chamber, thevacuum chamber being connected with the vacuum chamber of the ion beamdevice with at least one vibration free mechanism component in between,and an area cooled by the cooling agent and the emitter tip beingconnected with at least one shape changeable mechanism component inbetween.

(13) The gas field ion source according to (1), wherein a mechanism forvarying a conductance for vacuum exhausting the gas molecule ionizationchamber is a valve operable from outside the vacuum chamber, and ismechanically separable with a wall structure body of the ionizationchamber.

(14) The gas field ion source according to (1), further including aresistive heater for heating the gas molecule ionization chamber,wherein mechanical disconnection with a plurality of electric wiringsconnected to the resistive heater is carried out by operating at leastone of the plurality of electric wirings from outside in vacuum.

(15) The gas field ion source according to (1), wherein a cooling agentof the cooling mechanism is a cooling agent in which a cooling mediumgas, which is in a gas state under normal temperature and atmospherepressure, is in a solid state.

(16) An ion microscope comprising:

the gas field ion source according to any one of (1) to (5) or (13) to(15);

a lens system for focusing ions extracted from the gas field ion source;

a secondary particle detector for detecting secondary particles; and

an image display unit for displaying an ion microscope image.

According to the present invention, the following ion microscope, ionbeam device, and an ion beam examination device are disclosed.

(17) An ion beam device comprising a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, and a cooling mechanism of the emittertip, for supplying gas molecules to a vicinity of a distal end of theemitter tip and ionizing the gas molecules with an electric field at thedistal end of the emitter tip; an objective lens and a lens for focusingan ion beam extracted from the emitter tip; a sample chamberincorporating a sample; and a secondary particle detector for detectingsecondary particles released from the sample; wherein an ion beamdiameter can be focused to 0.5 nm by reducing a distance from a distalend of the objective lens to a surface of the sample to less than 2 mm.

(18) An ion microscope comprising a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, and a cooling mechanism of the emittertip, for supplying gas molecules to a vicinity of a distal end of theemitter tip and ionizing the gas molecules with an electric field at thedistal end of the emitter tip; a lens system for focusing an ion beamextracted from the emitter tip; a sample chamber incorporating a sample;and a secondary particle detector for detecting secondary particlesreleased from the sample; wherein the sample chamber is heated up toabout 200° C. to have a degree of vacuum of the sample chamber tosmaller than or equal to 10⁻⁷ Pa at the maximum.

(19) An ion microscope comprising a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, and a cooling mechanism of the emittertip, for supplying gas molecules to a vicinity of a distal end of theemitter tip and ionizing the gas molecules with an electric field at thedistal end of the emitter tip; a lens system for focusing an ion beamextracted from the emitter tip; a sample chamber incorporating a sample;a secondary particle detector for detecting secondary particles releasedfrom the sample; and a vacuum pump for vacuum exhausting the samplechamber; wherein a main vacuum pump for vacuum exhausting the samplechamber during a microscope image observation with the ion microscopeincludes one of a sublimation pump, a non-evaporative getter pump, anion pump, a noble pump, or an excel pump.

(20) An ion microscope comprising a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, and a cooling mechanism of the emittertip, for supplying gas molecules to a vicinity of a distal end of theemitter tip and ionizing the gas molecules with an electric field at thedistal end of the emitter tip; a vacuum pump for vacuum exhausting thegas field ion source; a lens system for focusing an ion beam extractedfrom the emitter tip; a sample chamber incorporating a sample; and asecondary particle detector for detecting secondary particles releasedfrom the sample; wherein a main vacuum pump for vacuum exhausting thegas field ion source during a microscope image observation with the ionmicroscope includes one of a sublimation pump, a non-evaporative getterpump and an ion pump, a noble pump or an excel pump.

(21) An ion beam device comprising a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, a container of a liquid freezingmixture for a cooling mechanism of the emitter tip, and a vacuum pumpfor vacuum exhausting the container of the liquid freezing mixture, forsupplying gas molecules to a vicinity of a distal end of the emitter tipand ionizing the gas molecules with an electric field at the distal endof the emitter tip; a lens system for focusing an ion beam extractedfrom the emitter tip; a sample chamber incorporating a sample; and asecondary particle detector for detecting secondary particles releasedfrom the sample; further including a control device for controlling theoperation of the vacuum pump by a vacuum degree measurement or atemperature measurement of the container of the liquid freezing mixture,and controlling the temperature of the container of the liquid freezingmixture.

(22) An ion beam device comprising a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, a container of a liquid freezingmixture for a cooling mechanism of the emitter tip, and a vacuum pumpfor vacuum exhausting the container of the liquid freezing mixture, forsupplying gas molecules to a vicinity of a distal end of the emitter tipand ionizing the gas molecules with an electric field at the distal endof the emitter tip; a lens system for focusing an ion beam extractedfrom the emitter tip; a sample chamber incorporating a sample; and asecondary particle detector for detecting secondary particles releasedfrom the sample; wherein

the cooling mechanism is a refrigerator for cooling a stage of therefrigerator with coldness of a coldness generation means for generatingthe coldness by expanding a high pressure gas generated in a compressorunit, a cover being arranged on the compressor unit for generating thehigh pressure gas to reduce noise from the compressor unit of the gas.

(23) An ion microscope comprising a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, a container of a liquid freezingmixture for a cooling mechanism of the emitter tip, and a vacuum pumpfor vacuum exhausting the container of the liquid freezing mixture, forsupplying gas molecules to a vicinity of a distal end of the emitter tipand ionizing the gas molecules with an electric field at the distal endof the emitter tip, a lens system for focusing an ion beam extractedfrom the emitter tip, a sample stage including at least two types ofmoving mechanisms with respect to at least two directions within an ionbeam irradiation plane, a sample chamber incorporating a sample placedon the sample stage, and a secondary particle detector for detectingsecondary particles released from the sample, the sample stage isscanning moved mechanically in two orthogonal directions, and thesecondary particles released from the sample are detected to obtain anion microscope image.

(24) The ion microscope described in (23), the sample stage including atleast two types of moving mechanisms with respect to at least twodirections within the ion beam irradiation plane includes a stage usingat least a piezoelectric element driving mechanism, an image resolutionof the ion microscope image being less than 0.5 nm.

(25) An ion beam device comprising a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, a cooling mechanism of the emitter tip,and a gas supply piping, for supplying gas molecules to a vicinity of adistal end of the emitter tip and ionizing the gas molecules with anelectric field at the distal end of the emitter tip; a lens system forfocusing an ion beam extracted from the emitter tip; a sample chamberincorporating a sample; a secondary particle detector for detectingsecondary particles released from the sample; and vacuum pump for vacuumexhausting the sample chamber; wherein

non-evaporative getter material is arranged in the supply piping usinginactive gas such as helium, neon, argon, krypton, and xenon.

(26) An ion beam device comprising a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, and a cooling mechanism of the emittertip, for supplying gas molecules to a vicinity of a distal end of theemitter tip and ionizing the gas molecules with an electric field at thedistal end of the emitter tip; an objective lens and a lens for focusingan ion beam extracted from the emitter tip; a sample chamberincorporating a sample; and a secondary particle detector for detectingsecondary particles released from the sample; wherein a high negativevoltage is applied to the emitter tip to extract electrons from theemitter tip and irradiate the sample, an X-ray or Auger electronreleased from the sample is detected to enable an element analysis, anda scanning ion image having a resolution of smaller than or equal to 1nm and an element analysis image are displayed side by side or in anoverlapping manner.

(27) An ion beam examination device comprising a gas field ion source,configured by a vacuum chamber, a vacuum exhaust mechanism, an emittertip that composes a needle-shaped anode and an extraction electrode thatcomposes a cathode in the vacuum chamber, and a cooling mechanism of theemitter tip, for supplying gas molecules to a vicinity of a distal endof the emitter tip and ionizing the gas molecules with an electric fieldat the distal end of the emitter tip; an objective lens and a lens forfocusing an ion beam extracted from the emitter tip; and a samplechamber incorporating a sample; and a unit for detecting secondaryparticles released from the sample and measuring a structural dimensionof a sample surface; wherein the structural dimension of thesemiconductor sample is measured with the accelerating voltage of theion beam at greater than or equal to 50 kV.

(28) The ion beam examination device according to (27), wherein hydrogengas is used.

(29) An ion beam examination device comprising a gas field ion source,configured by a vacuum chamber, a vacuum exhaust mechanism, an emittertip that composes a needle-shaped anode and an extraction electrode thatcomposes a cathode in the vacuum chamber, and a cooling mechanism of theemitter tip, for supplying gas molecules to a vicinity of a distal endof the emitter tip and ionizing the gas molecules with an electric fieldat the distal end of the emitter tip; an objective lens and a lens forfocusing an ion beam extracted from the emitter tip; and a samplechamber incorporating a sample; and a unit for detecting secondaryparticles released from the sample and measuring a structural dimensionof a sample surface; wherein the energy of ion beam is smaller than 1keV.

(30) An ion beam device comprising a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, and a cooling mechanism of the emittertip, for supplying gas molecules to a vicinity of a distal end of theemitter tip and ionizing the gas molecules with an electric field at thedistal end of the emitter tip; an objective lens and a lens for focusingan ion beam extracted from the emitter tip; a sample chamberincorporating a sample; and a secondary particle detector for detectingsecondary particles released from the sample; wherein a high negativevoltage is applied to the emitter tip to extract electrons from theemitter tip, passed through a compound objective lens in which amagnetic field lens and an electrostatic lens are combined andirradiated on the sample to detect an X-ray or an Auger electronreleased from the sample and enable an element analysis.

(31) A sample element analyzing method using an ion beam deviceincluding a gas field ion source, configured by a vacuum chamber, avacuum exhaust mechanism, an emitter tip that composes a needle-shapedanode and an extraction electrode that composes a cathode in the vacuumchamber, and a cooling mechanism of the emitter tip, for supplying gasmolecules to a vicinity of a distal end of the emitter tip and ionizingthe gas molecules with an electric field at the distal end of theemitter tip; an objective lens and a lens for focusing an ion beamextracted from the emitter tip; a sample chamber incorporating a sample;and a secondary particle detector for detecting secondary particlesreleased from the sample; the method comprising the steps of irradiatinga sample with an accelerating voltage of the ion beam at greater than orequal to 200 kV and a beam diameter narrowed to smaller than or equal to0.2 nm; energy analyzing ions Rutherford back scattered from the sample;and measuring a three-dimensional structure including a plane and adepth of the sample element in units of atoms.

(32) A sample element analyzing method using an ion beam deviceincluding a gas field ion source, configured by a vacuum chamber, avacuum exhaust mechanism, an emitter tip that composes a needle-shapedanode and an extraction electrode that composes a cathode in the vacuumchamber, and a cooling mechanism of the emitter tip, for supplying gasmolecules to a vicinity of a distal end of the emitter tip and ionizingthe gas molecules with an electric field at the distal end of theemitter tip; an objective lens and a lens for focusing an ion beamextracted from the emitter tip; a sample chamber incorporating a sample;and a secondary particle detector for detecting secondary particlesreleased from the sample; the method comprising the steps of irradiatinga sample at greater than or equal to 500 kV and a beam diameter narrowedto smaller than or equal to 0.2 nm; energy analyzing an X ray releasedfrom the sample; and performing a two-dimensional element analysis.

(33) An ion beam device including a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, and a cooling mechanism of the emittertip, for supplying gas molecules to a vicinity of a distal end of theemitter tip and ionizing the gas molecules with an electric field at thedistal end of the emitter tip; an objective lens and a lens for focusingan ion beam extracted from the emitter tip; a sample chamberincorporating a sample; and a secondary particle detector for detectingsecondary particles released from the sample; wherein the emitter tip iscooled to lower than or equal to 50 K, a magnification of projecting theion released from the emitter tip on the sample is made to smaller than0.2, and a vibration of a relative position of the emitter tip and thesample is made to smaller than or equal to 0.1 nm so that a scanning ionimage resolution is smaller than or equal to 0.2 nm.

(34) An ion beam device including a gas field ion source, configured bya vacuum chamber, a vacuum exhaust mechanism, an emitter tip thatcomposes a needle-shaped anode and an extraction electrode that composesa cathode in the vacuum chamber, and a cooling mechanism of the emittertip, for supplying gas molecules to a vicinity of a distal end of theemitter tip and ionizing the gas molecules with an electric field at thedistal end of the emitter tip; an objective lens and a lens for focusingan ion beam extracted from the emitter tip; a sample chamberincorporating a sample; and a secondary particle detector for detectingsecondary particles released from the sample; wherein the sample stageis a sample stage of side entry type, and the distal end has a structurecontacting the wall surface of the sample chamber.

(35) An ion beam device comprising:

a gas field ion source for generating an ion beam;

an ion irradiation light system for guiding the ion beam from the gasfield ion source to a sample;

a vacuum chamber for accommodating the gas field ion source and the ionirradiation light system;

a sample chamber for accommodating a sample stage for holding thesample; and

a cooling mechanism of a gas circulating method for cooling the gasfield ion source; wherein

the cooling mechanism includes a refrigerator, a piping for connectingthe refrigerator and the gas field ion source, a heat exchanger arrangedon the piping, and a circulating compressor for circulating liquidhelium in the piping, the piping being fixed and supported on a floor ora supporting body.

(36) An ion beam device comprising:

a gas field ion source for generating an ion beam;

an ion irradiation light system for guiding the ion beam from the gasfield ion source to a sample;

a vacuum chamber for accommodating the gas field ion source and the ionirradiation light system;

a sample chamber for accommodating a sample stage for holding a sample;and

a cooling mechanism for cooling the gas field ion source; wherein

the cooling mechanism is a coldness generation means for generatingcoldness by expanding a first high pressure gas generated in acompressor unit, and a cooling mechanism for cooling a body to be cooledwith helium gas or a second moving cooling medium cooled with thecoldness of the coldness generation means and circulated with thecompressor unit.

(37) An ion beam device comprising:

a gas field ion source for generating an ion beam;

an ion irradiation light system for guiding the ion beam from the gasfield ion source to a sample;

a vacuum chamber for accommodating the gas field ion source and the ionirradiation light system;

a sample chamber for accommodating a sample stage for holding a sample;

a cooling mechanism for cooling the gas field ion source; and

a base plate for supporting the gas field ion source, the vacuumchamber, and the sample chamber; wherein a mechanism for magnetic shieldis arranged on an ion beam irradiation path.

(38) An ion beam device comprising:

a gas field ion source for generating an ion beam;

an ion irradiation light system for guiding the ion beam from the gasfield ion source to a sample;

a vacuum chamber for accommodating the gas field ion source and the ionirradiation light system;

a sample chamber for accommodating a sample stage for holding a sample;

a cooling mechanism for cooling the gas field ion source; and

a base plate for supporting the gas field ion source, the vacuumchamber, and the sample chamber; wherein

a main material of one of the vacuum chambers of the gas field ionsource and the ion beam irradiation system, and the sample chamber isiron or permalloy, and the resolution of the scanning ion image issmaller than or equal to 0.5 nm.

1. A gas field ion source comprising: an acicular anode emitter tip; agas molecule ionization chamber to supply gas molecules to the vicinityof the apex of the emitter tip and ionize the gas molecules by anelectric field at the apex of the emitter tip; and a vacuuming system,wherein the gas molecules are hydrogen molecules, neon molecules, argonmolecules, krypton molecules or xenon molecules, and the vacuumingsystem includes a nonvolatile getter pump.